make it compile under MSN vc. Unfortunately it has a weird crash at boot :(

- Lots of indenting changes
- VC++ is strict with variadic macros
- VC++ does not accept unistd.h
- new interface for walltime
- VC++ does not seem to have support for integer overflow.
- VC++ defines YENV_REG?
- no access flags, x permissions ignored.
- new FindGMP supporting MPIR
- make horus optional (c++ is hard).

include/pl-types.h

@@ -37,9 +37,7 @@ typedef int     (*PL_agc_hook_t)(atom_t);
 typedef uintptr_t	foreign_t;	/* return type of foreign functions */
 typedef wchar_t pl_wchar_t;             /* wide character support */
 #include <inttypes.h>			/* more portable than stdint.h */
-#if  !defined(_MSC_VER)
 typedef uintptr_t	PL_fid_t;	/* opaque foreign context handle */
-#endif
 typedef int  (*PL_dispatch_hook_t)(int fd);
 typedef void *pl_function_t;