all: Simplify mp_int_t/mp_uint_t definition.

Assuming proper C99 language support, we can select "the int type as big as
a pointer" (most of the time) or "the 64-bit int type" (nanboxing with
REPR_D), and then define everything else automatically.

This simplifies port configuration files.  And the types can still be
overridden if needed.

Signed-off-by: Jeff Epler <jepler@unpythonic.net>

ports/cc3200/mpconfigport.h

@@ -130,8 +130,6 @@
 #define MICROPY_MAKE_POINTER_CALLABLE(p)            ((void *)((mp_uint_t)(p) | 1))
 #define MP_SSIZE_MAX                                (0x7FFFFFFF)
 
-typedef int32_t mp_int_t;                           // must be pointer size
-typedef unsigned int mp_uint_t;                     // must be pointer size
 typedef long mp_off_t;
 
 #define MICROPY_EVENT_POLL_HOOK                     __WFI();