Turn MOD from function to macro.

I experimented with expanding it to ((N % M) everywhere, but in context
the MOD(N, M) notation seems easier to read.

misc.c

@@ -698,7 +698,4 @@ void DATIME(long* d, long* t)
     *t = (long) tv.tv_usec;
 }
 
-long MOD(long n, long m) 
-{
-    return(n%m);
-}
+/* end */