Do not forward declare OBJC types.

We have to disable forward declaration of objective-c
types in Qt when building chromium code.
Chromium does have different, incompatible
forward declarations.

Change-Id: Ib7f7e9839e5c85d758d1e5bb921e67c57a55c4ef
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Mac: INCLUDEPATH fix

Something seems to be busted with 5.2 lately. Specifically on Mac.
Work around the problem for now.

Change-Id: I4180257f31e67d02d46e26808e8b044f3b0c0cd2
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>