Added a naive NOLINT implementation.

Summary:
Added a naive NOLINT implementation. It doesn't care about specific
linter categories, just the "// NOLINT" on the same line as a diagnostic.

Reviewers: klimek

Reviewed By: klimek

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2896

llvm-svn: 202452