[PATCH] Don't warn about Unicode characters in -E mode

[Jordan Rose]

  r174081 brought an update to not warn at all in preprocessor directives, because some people do silly things with macros and pragmas. They'll end up with the default tok::unknown error and a caret if the macro gets expanded in the wrong place, just no nice "this is Unicode, did you really mean that?" note.

  Closing on Phab.

http://llvm-reviews.chandlerc.com/D346