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).

os/streams.c

@@ -881,8 +881,14 @@ void Yap_CloseStreams(int loud) {
   for (sno = 3; sno < MaxStreams; ++sno) {
     if (GLOBAL_Stream[sno].status & Free_Stream_f)
       continue;
-    if ((GLOBAL_Stream[sno].status & Popen_Stream_f))
-      pclose(GLOBAL_Stream[sno].file);
+	if ((GLOBAL_Stream[sno].status & Popen_Stream_f)) {
+#if _MSC_VER
+
+		_pclose(GLOBAL_Stream[sno].file);
+#else
+		pclose(GLOBAL_Stream[sno].file);
+#endif
+	}
     if (GLOBAL_Stream[sno].status & (Pipe_Stream_f | Socket_Stream_f))
       close(GLOBAL_Stream[sno].u.pipe.fd);
 #if USE_SOCKET