[Parser] Handle __pragma(pack, etc. after type definitions

Support certain MS pragmas right after the closing curly brace of a
class.  Clang did not expect __pragma in this position.

This fixes PR28094.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272628 91177308-0d34-0410-b5e6-96231b3b80d8