nhclose

Changes to be committed:
	modified:   include/extern.h
	modified:   src/bones.c
	modified:   src/do.c
	modified:   src/files.c
	modified:   src/music.c
	modified:   src/restore.c
	modified:   src/save.c
	modified:   sys/share/pcmain.c
	modified:   sys/share/pcsys.c
	modified:   sys/share/pcunix.c

In order to get level file locking correctly again post 3.4.3
with the newer compilers for windows, I had to funnel close()
calls to an intercepting routine.

I had two choices:

1. Surround every close() in at least 9 source files with messy:
	#ifdef WIN32
		nhclose(fd);
	#else
		close(fd);
	#endif

OR

2. Replace every close() with nhclose() and
   deal with the special code in the nhclose()
   version for windows, while just calling
   close() for other platforms (in files.c).

   It is also possible, although not done in this commit,
   to
	#define nhclose(fd) close(fd)
   in a header file for non-windows, rather than funnel
   though a real nhclose() function in files.c.

include/extern.h

@@ -743,6 +743,7 @@ E boolean NDECL(recover_savefile);
 #ifdef SYSCF_FILE
 E void NDECL(assure_syscf_file);
 #endif
+E int FDECL(nhclose, (int));
 #ifdef HOLD_LOCKFILE_OPEN
 E void NDECL(really_close);
 #endif