[clang-tidy] Added -fix-errors option

Summary:
Added -fix-errors option to allow applying fixes when compiler errors
are present. Without this flag -fix would bail out if there are compiler errors.
This is needed to avoid applying wrong fixes if Clang fails to recover from
compilation errors correctly.

Reviewers: djasper, klimek

Reviewed By: klimek

Subscribers: curdeius, cfe-commits

Differential Revision: http://reviews.llvm.org/D6059