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).

C/threads.c

@@ -30,7 +30,9 @@ static char     SccsId[] = "%W% %G%";
 #include "yapio.h"
 #include "blobs.h"
 #include <stdio.h>
+#if HAVE_UNISTD_H
 #include <unistd.h>
+#endif
 #if HAVE_STRING_H
 #include <string.h>
 #endif