Clang-tidy: don't create ASTConsumers not needed for the set of checks we perform.

Summary:
This doesn't have any significant effect on the performance, but it
looks like a good thing to do.

Reviewers: djasper, klimek

Reviewed By: klimek

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2763

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@201340 91177308-0d34-0410-b5e6-96231b3b80d8
Re-add the '!' removed by mistake.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@201343 91177308-0d34-0410-b5e6-96231b3b80d8