Replace fDATIME with ANSI/POSIX clock_gettime(). Rip out DOS/AMIGA shims.

The thinking here is that we simplify life by going pure ANSI/POSIX.
This is a text game.  If it ever runs on anything but Unix again it's
almost certain to be on something like WSL that supplies a
POSIX-conformant text console.

main.c

@@ -8,9 +8,6 @@
 #include "main.h"
 
 #include "misc.h"
-#ifdef __MSDOS__
-#include "alloc.h"
-#endif
 
 #define TRUE  (0==0)
 #define FALSE (0!=0)