Rename rt_* to mp_*.

Mostly just a global search and replace.  Except rt_is_true which
becomes mp_obj_is_true.

Still would like to tidy up some of the names, but this will do for now.
diff --git a/unix/ffi.c b/unix/ffi.c
index 9a4c035..71fb0b6 100644
--- a/unix/ffi.c
+++ b/unix/ffi.c
@@ -128,10 +128,10 @@
     o->func = sym;
     o->rettype = *rettype;
 
-    mp_obj_t iterable = rt_getiter(args[3]);
+    mp_obj_t iterable = mp_getiter(args[3]);
     mp_obj_t item;
     int i = 0;
-    while ((item = rt_iternext(iterable)) != MP_OBJ_NULL) {
+    while ((item = mp_iternext(iterable)) != MP_OBJ_NULL) {
         o->params[i++] = get_ffi_type(item);
     }
 
@@ -149,7 +149,7 @@
     for (int i = 0; i < cif->nargs; i++) {
         pyargs[i] = mp_obj_new_int(*(int*)args[i]);
     }
-    mp_obj_t res = rt_call_function_n_kw(func, cif->nargs, 0, pyargs);
+    mp_obj_t res = mp_call_function_n_kw(func, cif->nargs, 0, pyargs);
 
     *(ffi_arg*)ret = mp_obj_int_get(res);
 }
@@ -165,10 +165,10 @@
 
     o->rettype = *rettype;
 
-    mp_obj_t iterable = rt_getiter(paramtypes_in);
+    mp_obj_t iterable = mp_getiter(paramtypes_in);
     mp_obj_t item;
     int i = 0;
-    while ((item = rt_iternext(iterable)) != MP_OBJ_NULL) {
+    while ((item = mp_iternext(iterable)) != MP_OBJ_NULL) {
         o->params[i++] = get_ffi_type(item);
     }
 
@@ -348,8 +348,8 @@
 
 void ffi_init() {
     mp_obj_t m = mp_obj_new_module(QSTR_FROM_STR_STATIC("ffi"));
-    rt_store_attr(m, MP_QSTR_open, (mp_obj_t)&mod_ffi_open_obj);
-    rt_store_attr(m, QSTR_FROM_STR_STATIC("callback"), (mp_obj_t)&mod_ffi_callback_obj);
+    mp_store_attr(m, MP_QSTR_open, (mp_obj_t)&mod_ffi_open_obj);
+    mp_store_attr(m, QSTR_FROM_STR_STATIC("callback"), (mp_obj_t)&mod_ffi_callback_obj);
     // there would be as_bytes, but bytes currently is value, not reference type!
-    rt_store_attr(m, QSTR_FROM_STR_STATIC("as_bytearray"), (mp_obj_t)&mod_ffi_as_bytearray_obj);
+    mp_store_attr(m, QSTR_FROM_STR_STATIC("as_bytearray"), (mp_obj_t)&mod_ffi_as_bytearray_obj);
 }
diff --git a/unix/file.c b/unix/file.c
index f037b6f..948ec44 100644
--- a/unix/file.c
+++ b/unix/file.c
@@ -140,7 +140,7 @@
 
 void file_init() {
     mp_obj_t m_sys = mp_obj_new_module(MP_QSTR_sys);
-    rt_store_attr(m_sys, MP_QSTR_stdin, fdfile_new(STDIN_FILENO));
-    rt_store_attr(m_sys, MP_QSTR_stdout, fdfile_new(STDOUT_FILENO));
-    rt_store_attr(m_sys, MP_QSTR_stderr, fdfile_new(STDERR_FILENO));
+    mp_store_attr(m_sys, MP_QSTR_stdin, fdfile_new(STDIN_FILENO));
+    mp_store_attr(m_sys, MP_QSTR_stdout, fdfile_new(STDOUT_FILENO));
+    mp_store_attr(m_sys, MP_QSTR_stderr, fdfile_new(STDERR_FILENO));
 }
diff --git a/unix/main.c b/unix/main.c
index 6b25988..ffbdbb7 100644
--- a/unix/main.c
+++ b/unix/main.c
@@ -85,7 +85,7 @@
     // execute it
     nlr_buf_t nlr;
     if (nlr_push(&nlr) == 0) {
-        rt_call_function_0(module_fun);
+        mp_call_function_0(module_fun);
         nlr_pop();
     } else {
         // uncaught exception
@@ -278,7 +278,7 @@
 #endif
 
     qstr_init();
-    rt_init();
+    mp_init();
 
     char *home = getenv("HOME");
     char *path = getenv("MICROPYPATH");
@@ -292,9 +292,9 @@
             p++;
         }
     }
-    sys_path = mp_obj_new_list(path_num, NULL);
+    mp_sys_path = mp_obj_new_list(path_num, NULL);
     mp_obj_t *path_items;
-    mp_obj_list_get(sys_path, &path_num, &path_items);
+    mp_obj_list_get(mp_sys_path, &path_num, &path_items);
     path_items[0] = MP_OBJ_NEW_QSTR(MP_QSTR_);
     char *p = path;
     for (int i = 1; i < path_num; i++) {
@@ -315,15 +315,15 @@
     }
 
     mp_obj_t m_sys = mp_obj_new_module(MP_QSTR_sys);
-    rt_store_attr(m_sys, MP_QSTR_path, sys_path);
+    mp_store_attr(m_sys, MP_QSTR_path, mp_sys_path);
     mp_obj_t py_argv = mp_obj_new_list(0, NULL);
-    rt_store_attr(m_sys, MP_QSTR_argv, py_argv);
+    mp_store_attr(m_sys, MP_QSTR_argv, py_argv);
 
-    rt_store_name(qstr_from_str("test"), test_obj_new(42));
-    rt_store_name(qstr_from_str("mem_info"), rt_make_function_n(0, mem_info));
-    rt_store_name(qstr_from_str("qstr_info"), rt_make_function_n(0, qstr_info));
+    mp_store_name(qstr_from_str("test"), test_obj_new(42));
+    mp_store_name(qstr_from_str("mem_info"), mp_make_function_n(0, mem_info));
+    mp_store_name(qstr_from_str("qstr_info"), mp_make_function_n(0, qstr_info));
 #if MICROPY_ENABLE_GC
-    rt_store_name(qstr_from_str("gc"), (mp_obj_t)&pyb_gc_obj);
+    mp_store_name(qstr_from_str("gc"), (mp_obj_t)&pyb_gc_obj);
 #endif
 
     file_init();
@@ -344,8 +344,8 @@
     // test_obj.attr = 42
     mp_obj_t test_class_type, test_class_instance;
     test_class_type = mp_obj_new_type(QSTR_FROM_STR_STATIC("TestClass"), mp_const_empty_tuple, mp_obj_new_dict(0));
-    rt_store_name(QSTR_FROM_STR_STATIC("test_obj"), test_class_instance = rt_call_function_0(test_class_type));
-    rt_store_attr(test_class_instance, QSTR_FROM_STR_STATIC("attr"), mp_obj_new_int(42));
+    mp_store_name(QSTR_FROM_STR_STATIC("test_obj"), test_class_instance = mp_call_function_0(test_class_type));
+    mp_store_attr(test_class_instance, QSTR_FROM_STR_STATIC("attr"), mp_obj_new_int(42));
 
     /*
     printf("bytes:\n");
@@ -378,7 +378,7 @@
                 free(basedir);
             }
             for (int i = a; i < argc; i++) {
-                rt_list_append(py_argv, MP_OBJ_NEW_QSTR(qstr_from_str(argv[i])));
+                mp_list_append(py_argv, MP_OBJ_NEW_QSTR(qstr_from_str(argv[i])));
             }
             do_file(argv[a]);
             executed = true;
@@ -390,7 +390,7 @@
         do_repl();
     }
 
-    rt_deinit();
+    mp_deinit();
 
     //printf("total bytes = %d\n", m_get_total_bytes_allocated());
     return 0;
diff --git a/unix/socket.c b/unix/socket.c
index 04c1d10..ee74ea0 100644
--- a/unix/socket.c
+++ b/unix/socket.c
@@ -314,7 +314,7 @@
     }
     assert(addr);
 
-    mp_obj_t list = rt_build_list(0, NULL);
+    mp_obj_t list = mp_build_list(0, NULL);
     for (; addr; addr = addr->ai_next) {
         mp_obj_tuple_t *t = mp_obj_new_tuple(5, NULL);
         t->items[0] = MP_OBJ_NEW_SMALL_INT((machine_int_t)addr->ai_family);
@@ -328,7 +328,7 @@
             t->items[3] = mp_const_none;
         }
         t->items[4] = mp_obj_new_bytearray(addr->ai_addrlen, addr->ai_addr);
-        rt_list_append(list, t);
+        mp_list_append(list, t);
     }
     return list;
 }
@@ -366,15 +366,15 @@
 
 void microsocket_init() {
     mp_obj_t m = mp_obj_new_module(MP_QSTR_microsocket);
-    rt_store_attr(m, MP_QSTR_socket, (mp_obj_t)&microsocket_type);
+    mp_store_attr(m, MP_QSTR_socket, (mp_obj_t)&microsocket_type);
 #if MICROPY_SOCKET_EXTRA
-    rt_store_attr(m, MP_QSTR_sockaddr_in, (mp_obj_t)&sockaddr_in_type);
-    rt_store_attr(m, MP_QSTR_htons, (mp_obj_t)&mod_socket_htons_obj);
-    rt_store_attr(m, MP_QSTR_inet_aton, (mp_obj_t)&mod_socket_inet_aton_obj);
-    rt_store_attr(m, MP_QSTR_gethostbyname, (mp_obj_t)&mod_socket_gethostbyname_obj);
+    mp_store_attr(m, MP_QSTR_sockaddr_in, (mp_obj_t)&sockaddr_in_type);
+    mp_store_attr(m, MP_QSTR_htons, (mp_obj_t)&mod_socket_htons_obj);
+    mp_store_attr(m, MP_QSTR_inet_aton, (mp_obj_t)&mod_socket_inet_aton_obj);
+    mp_store_attr(m, MP_QSTR_gethostbyname, (mp_obj_t)&mod_socket_gethostbyname_obj);
 #endif
-    rt_store_attr(m, MP_QSTR_getaddrinfo, (mp_obj_t)&mod_socket_getaddrinfo_obj);
+    mp_store_attr(m, MP_QSTR_getaddrinfo, (mp_obj_t)&mod_socket_getaddrinfo_obj);
     for (const struct sym_entry *p = constants; p->sym != NULL; p++) {
-        rt_store_attr(m, QSTR_FROM_STR_STATIC(p->sym), MP_OBJ_NEW_SMALL_INT((machine_int_t)p->val));
+        mp_store_attr(m, QSTR_FROM_STR_STATIC(p->sym), MP_OBJ_NEW_SMALL_INT((machine_int_t)p->val));
     }
 }
diff --git a/unix/time.c b/unix/time.c
index 7d25b3d..fb52133 100644
--- a/unix/time.c
+++ b/unix/time.c
@@ -43,7 +43,7 @@
 
 void time_init() {
     mp_obj_t m = mp_obj_new_module(QSTR_FROM_STR_STATIC("time"));
-    rt_store_attr(m, QSTR_FROM_STR_STATIC("time"), (mp_obj_t)&mod_time_time_obj);
-    rt_store_attr(m, QSTR_FROM_STR_STATIC("clock"), (mp_obj_t)&mod_time_clock_obj);
-    rt_store_attr(m, QSTR_FROM_STR_STATIC("sleep"), (mp_obj_t)&mod_time_sleep_obj);
+    mp_store_attr(m, QSTR_FROM_STR_STATIC("time"), (mp_obj_t)&mod_time_time_obj);
+    mp_store_attr(m, QSTR_FROM_STR_STATIC("clock"), (mp_obj_t)&mod_time_clock_obj);
+    mp_store_attr(m, QSTR_FROM_STR_STATIC("sleep"), (mp_obj_t)&mod_time_sleep_obj);
 }