Rename all the M_* flags to be namespace qualified enums, and switch

Rename all the M_* flags to be namespace qualified enums, and switch
all clients over to using predicates instead of these flags directly.
These are now private values which are only to be used to statically
initialize the tables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45692 91177308-0d34-0410-b5e6-96231b3b80d8