Clang: handle ifdeffed-out blocks in the highlighter.

Change-Id: Ib206ee97de1d87a16735d996871ae1f2dc66b919
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
Clang: use the fallback project part when no other is available.

Change-Id: I783c54ba51230f8d7dbf22b95d5b4645f05024a3
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>