Summary:
This patch fixes a bug where clang-format will align newly broken trailing
comments even if this will make them exceed the line limit. The bug was caused
by a combination of unsigned arithmetic overflow and an imprecise computation
of the length of broken comment lines.

Reviewers: djasper, alexfh

Reviewed By: alexfh

Subscribers: klimek

Differential Revision: https://reviews.llvm.org/D33830

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@304687 91177308-0d34-0410-b5e6-96231b3b80d8