Allow teleportation onto the Vibrating Square

It's a minor annoyance when you forget you can't do this in vanilla and
then get relocated somewhere random on the level. Since it's not a
harmful "trap", just allow the adventurer to teleport directly onto it.

doc/fixes37.0

@@ -15,6 +15,7 @@ message "your knapsack can't accomodate any more items" when picking stuff up
 	pending; vary the message rather than add more convoluted pickup code
 function calls made from mapglyph based on dungeon level are now called once
 	per level
+allow teleporting onto the vibrating square
 
 
 Fixes to Pre-3.7.0 Problems that Were Exposed Via git Repository

src/teleport.c

@@ -260,8 +260,13 @@ teleok(x, y, trapok)
 register int x, y;
 boolean trapok;
 {
-    if (!trapok && t_at(x, y))
-        return FALSE;
+    if (!trapok) {
+        /* allow teleportation onto vibrating square, it's not a real trap */
+        struct trap *trap = t_at(x, y);
+        if (trap && trap->ttyp != VIBRATING_SQUARE) {
+            return FALSE;
+        }
+    }
     if (!goodpos(x, y, &g.youmonst, 0))
         return FALSE;
     if (!tele_jump_ok(u.ux, u.uy, x, y))