Remove QT_{BEGIN,END}_HEADER macro usage

The macro was made empty in qtbase/ba3dc5f3b56d1fab6fe37fe7ae08096d7dc68bcb
and is no longer necessary or used.

Change-Id: I208ae87694deeb4edc73bb1a4be314c30861910f
Discussed-on: http://lists.qt-project.org/pipermail/development/2013-January/009284.html


Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>