Fix compiler warning on shift overflow.

In file included from /Users/erik/dev/qt5-stable/qtbase/include/QtXmlPatterns/5.0.0/QtXmlPatterns/private/qcoloroutput_p.h:1:
/Users/erik/dev/qt5-stable/qtbase/include/QtXmlPatterns/5.0.0/QtXmlPatterns/private/../../../../../../qtxmlpatterns/src/xmlpatterns/api/qcoloroutput_p.h:74:60: warning: signed
      shift result (0xFFFFF00000) requires 41 bits to represent, but 'int' only has 32 bits [-Wshift-overflow]
            BackgroundMask  = ((1 << BackgroundShift) - 1) << BackgroundShift
                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~

Change-Id: Id8b1d9748dd94350d42889b36c61c163786beb38
Reviewed-by: Lars Knoll <lars.knoll@digia.com>