cham changes (trunk only)

This is a foundation patch for patches to follow.
- use a full short index for mon->cham field.
- The current system of providing CHAM_XXX values
  was limited to the 3 bits allocated in the bitfield and invalidated
  save/bones if the field was expanded.
- The current system didn't provide an easy backwards  change
  if multiple monster types wanted to use the bit, there was a one
  to one mapping:  For instance, if you wanted a CHAM_VAMPIRE,
  and you wanted vampires, vampire lords, and Vlad to use it, you
  would have to have CHAM_VAMPIRE, CHAM_VAMPIRE_LORD,
  and CHAM_VLAD defined to achieve that with the one-to-one backward
  mapping.
- This new way just uses the mon[] index in the mon->cham field and
  eliminates the need for CHAM_XXX  (CHAM_ORDINARY is still used).
- no longer requires the cham_to_pm mappings

include/monflag.h

@@ -123,6 +123,7 @@
 #define M2_PRINCE	0x00000800L	/* is an overlord to its kind */
 #define M2_MINION	0x00001000L	/* is a minion of a deity */
 #define M2_GIANT	0x00002000L	/* is a giant */
+#define M2_SHAPESHIFTER	0x00004000L	/* is a shapeshifting species */
 #define M2_MALE		0x00010000L	/* always male */
 #define M2_FEMALE	0x00020000L	/* always female */
 #define M2_NEUTER	0x00040000L	/* neither male nor female */