Convert the vibrating square to a trap

Patch due to ais523 in NetHack 4.

This is not ready to be merged yet; the vibrating square needs a tile
image for tiles builds.

include/trap.h

@@ -78,6 +78,7 @@ extern struct trap *ftrap;
 #define MAGIC_TRAP	20
 #define ANTI_MAGIC	21
 #define POLY_TRAP	22
-#define TRAPNUM 23
+#define VIBRATING_SQUARE 23
+#define TRAPNUM 24
 
 #endif /* TRAP_H */