vampires now shapeshift [trunk only]

- can shift into fog clouds, vampire bats, and vampire lords into wolves
- after being "killed" in shifted form, they transform back rather than get
  destroyed, and you must take them on in vampire form to defeat them
- can deliberately shift into fog clouds to pass under closed doors

include/monst.h

@@ -176,5 +176,7 @@ struct monst {
 
 #define DEADMONSTER(mon)	((mon)->mhp < 1)
 #define is_starting_pet(mon)	((mon)->m_id == context.startingpet_mid)
-
+#define is_vampshifter(mon)	((mon)->cham == PM_VAMPIRE || \
+				 (mon)->cham == PM_VAMPIRE_LORD || \
+				 (mon)->cham == PM_VLAD_THE_IMPALER)
 #endif /* MONST_H */