Add "REQUIRES-ANY" feature test

Summary:
This patch adds a "REQUIRES-ANY" feature test that is disjunctive. This marks a test as `UNSUPPORTED` if none of the specified features are available.

Libc++ has the need to write feature test such as `// REQUIRES-ANY: c++98, c++03`  when testing of behavior that is specific to older dialects but has since changed.


Reviewers: rnk, ddunbar

Subscribers: ddunbar, probinson, llvm-commits, cfe-commits

Differential Revision: http://reviews.llvm.org/D20757

llvm-svn: 271468