Fix movecmd always returning a direction

My recent commit broke the 'm' (menu request) -prefix, because
a thinko in movecmd made it always return a direction.

src/cmd.c

@@ -3707,7 +3707,7 @@ movecmd(char sym, int mode)
         char *mvkeys = (mode == MV_WALK) ? g.Cmd.move :
             ((mode == MV_RUN) ? g.Cmd.run : g.Cmd.rush);
 
-        for (d = 0; d < N_DIRS; d++) {
+        for (d = N_DIRS; d > DIR_ERR; d--) {
             if (mode == MV_ANY) {
                 if (sym == g.Cmd.move[d]
                     || sym == g.Cmd.rush[d]