This improves ObjC support:
- by recognising additional mimetypes (also in the source formatter)
- by changing the logic in argsForSession() such that the ObjC and ObjC++ mode arguments are appended to the other C/C++ arguments rather than replacing them.
Those are probably the main changes that give a significant improvement. In addition, I added code for handling two more CXCursor_* types (a bit via educated guessing). Handling CXCursor_BlockExpr as a lambda expr. seems rather evident, it is much less clear how to handle CXCursor_ObjCMessageExpr as I couldn't find a generic C/C++ expression handler (nor a corresponding CXCursor type, btw).