Rename machine_(u)int_t to mp_(u)int_t.

See discussion in issue #50.
diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index cf7896f..da02b1e 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -198,7 +198,7 @@
             case MP_BINARY_OP_RSHIFT:
             case MP_BINARY_OP_INPLACE_RSHIFT: {
                 // TODO check conversion overflow
-                machine_int_t irhs = mpz_as_int(zrhs);
+                mp_int_t irhs = mpz_as_int(zrhs);
                 if (irhs < 0) {
                     nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "negative shift count"));
                 }
@@ -241,7 +241,7 @@
     }
 }
 
-mp_obj_t mp_obj_new_int(machine_int_t value) {
+mp_obj_t mp_obj_new_int(mp_int_t value) {
     if (MP_SMALL_INT_FITS(value)) {
         return MP_OBJ_NEW_SMALL_INT(value);
     }
@@ -254,7 +254,7 @@
     return o;
 }
 
-mp_obj_t mp_obj_new_int_from_uint(machine_uint_t value) {
+mp_obj_t mp_obj_new_int_from_uint(mp_uint_t value) {
     // SMALL_INT accepts only signed numbers, of one bit less size
     // than word size, which totals 2 bits less for unsigned numbers.
     if ((value & (WORD_MSBIT_HIGH | (WORD_MSBIT_HIGH >> 1))) == 0) {
@@ -270,7 +270,7 @@
     return o;
 }
 
-machine_int_t mp_obj_int_get(mp_const_obj_t self_in) {
+mp_int_t mp_obj_int_get(mp_const_obj_t self_in) {
     if (MP_OBJ_IS_SMALL_INT(self_in)) {
         return MP_OBJ_SMALL_INT_VALUE(self_in);
     } else {
@@ -279,12 +279,12 @@
     }
 }
 
-machine_int_t mp_obj_int_get_checked(mp_const_obj_t self_in) {
+mp_int_t mp_obj_int_get_checked(mp_const_obj_t self_in) {
     if (MP_OBJ_IS_SMALL_INT(self_in)) {
         return MP_OBJ_SMALL_INT_VALUE(self_in);
     } else {
         const mp_obj_int_t *self = self_in;
-        machine_int_t value;
+        mp_int_t value;
         if (mpz_as_int_checked(&self->mpz, &value)) {
             return value;
         } else {