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

doc/fixes35.0

@@ -127,4 +127,5 @@ removed OVLx section dividers previously  used for TRAMPOLINE overlay system
 move all flags that are system or port specific from flag struct to sysflags 
 	struct which is used only if SYSFLAGS is defined
 all fields in flags struct are unconditionally present
+monst cham field now a short and uses mons[] index