[clang-tidy] Cleaning namespaces to be more consistant across checkers.

Summary:
The goal of the patch is to bring checkers in their appropriate namespace.
This path doesn't change any behavior.

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D19811

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@268264 91177308-0d34-0410-b5e6-96231b3b80d8
57 files changed