add a macro to ease conditional testing based on active window port

Add WINDOWPORT macro

example:
if (WINDOWPORT("tty"))
	pline("Look at me, I'm on tty at the moment!");

src/save.c

@@ -178,7 +178,7 @@ dosave0()
     dotcnt = 0;
     dotrow = 2;
     curs(WIN_MAP, 1, 1);
-    if (strncmpi("X11", windowprocs.name, 3))
+    if (!WINDOWPORT("X11"))
         putstr(WIN_MAP, 0, "Saving:");
 #endif
 #ifdef MFLOPPY
@@ -242,7 +242,7 @@ dosave0()
             dotrow++;
             dotcnt = 0;
         }
-        if (strncmpi("X11", windowprocs.name, 3)) {
+        if (!WINDOWPORT("X11")) {
             putstr(WIN_MAP, 0, ".");
         }
         mark_synch();