Refactor the Microsoft inheritance attribute handling so that it no longer has special treatment. Also fixes a minor bug where the attributes were being parsed as though they were GNU-style attributes when they were in fact keyword attributes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197629 91177308-0d34-0410-b5e6-96231b3b80d8