Tweak priorities for some types and macros:

Tweak priorities for some types and macros:
  - In Objective-C, we prefer BOOL to bool for historic reasons;
  slightly penalize "bool".
  - Treat Nil macro as a NULL pointer constant.
  - Treat YES, NO, true, and false macros as constants.
  - Treat the bool macro as a type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@114356 91177308-0d34-0410-b5e6-96231b3b80d8