Expand macros in pragmas with -fms-extensions and -E

gcc never expands macros in pragmas and MSVC always expands macros
before processing pragmas.  Clang usually allows macro expansion, except
in a handful of pragmas, most of which are handled by the lexer.

Also remove PPCallbacks for pragmas that are currently handled in the
parser.  Without a Parser, such as with clang -E, these callbacks would
never be called.

Fixes PR18576.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201821 91177308-0d34-0410-b5e6-96231b3b80d8