[NFC] Header cleanup

Summary: Removed unused headers, replaced some headers with forward class declarations

Patch by: Eugene <claprix@yandex.ru>

Differential Revision: https://reviews.llvm.org/D20100

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@275882 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
1 file changed