main.c has no dependency upon unixfork.h. (#79)

This avoids a bit of confusion, since unixfork.c isn't built into
the same executable as main.c. (It is part of `lde` instead.)

src/main.c

@@ -17,7 +17,6 @@ static char *id = "$Id: main.c,v 1.4 2001/12/26 22:17:03 sybalsky Exp $ Copyrigh
 
 #include "lispemul.h"
 #include "dbprint.h"
-#include "unixfork.h"
 
 #include <errno.h>
 #include <setjmp.h>