Change some parts of the core API to use mp_uint_t instead of uint/int.

Addressing issue #50, still some way to go yet.
diff --git a/py/objzip.c b/py/objzip.c
index 97a14eb..828d6bd 100644
--- a/py/objzip.c
+++ b/py/objzip.c
@@ -39,7 +39,7 @@
     mp_obj_t iters[];
 } mp_obj_zip_t;
 
-STATIC mp_obj_t zip_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+STATIC mp_obj_t zip_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 0, MP_OBJ_FUN_ARGS_MAX, false);
 
     mp_obj_zip_t *o = m_new_obj_var(mp_obj_zip_t, mp_obj_t, n_args);