Add support for the 'unless' matcher in the dynamic layer.

Summary: Add support for the 'unless' matcher in the dynamic layer.

Reviewers: klimek

CC: cfe-commits, revane, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D2247

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195466 91177308-0d34-0410-b5e6-96231b3b80d8