Select the keyboard push-subdirection with Tab.

Previously, the keyboard push-subdirection was selected irregularly
based on the exact angle of the map on the screen.

Change it to be consistently clockwise or counterclockwise, switching
with the Tab key.

Also, have the keyboard push-subdirection help display on all
pushable monsters.  Previously, it'd only show on Palace Guards
and Skeletons.

control.cpp

@@ -149,6 +149,7 @@ EX void movepckeydir(int d) {
   if(protect_memory()) return;
   
   movedir md = vectodir(move_destination_vec(d));
+  md.subdir = keybd_subdir ? 1 : -1;
     
   if(!canmove) movepcto(md), remission(); else movepcto(md);
   }
@@ -618,6 +619,10 @@ EX void handleKeyNormal(int sym, int uni) {
     else restart_game();
     }
 
+  if(sym == SDLK_TAB) {
+    keybd_subdir = !keybd_subdir;
+    }
+
   if(sym == SDLK_ESCAPE) {
     if(bow::fire_mode)
       bow::switch_fire_mode();