Make sure we have a Add/Remove/Has function for various thing that can have attribute.

Summary: This also deprecated the get attribute function familly.

Reviewers: Wallbraker, whitequark, joker.eph, echristo, rafael, jyknight

Subscribers: axw, joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19181

llvm-svn: 272504