Prior to making this a config option it was previously available on these
(and all other) ports, and it makes sense to keep it enabled for mpy-cross
as well as ports that have a decent amount of space for the code.
This type was used only for the typedef of mp_obj_t, which is now defined
by the object representation. So we can now remove this unused typedef,
to simplify the mpconfigport.h file.
When compiling with msys2's gcc there's no need to apply the binary fmode
so adjust the Makefile to reflect that.
When compiling with mingw we need to include malloc.h since there is no
alloca.h, and the 64bit detection in mpconfigport.h needs some adjustment.
