[clang-format] Emit absolute splits before lines for comments, try 2

[clang-format] Emit absolute splits before lines for comments, try 2

Summary:
This recommits https://reviews.llvm.org/D36956 with an update to the added test
case to not use raw string literals, since this makes gcc unhappy.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D37109

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@311672 91177308-0d34-0410-b5e6-96231b3b80d8