Adding support for symbian graphics resources.

Adding support for symbian graphics resources.

This enables us to convert from and to new Symbian type of
graphics resource, namely SgImage. This only supported with
the OpenVG graphics system.
On other graphics systems this will return null QPixmap.

Conflicts:
	src/corelib/global/qglobal.h
	src/gui/image/qpixmap.h
	src/gui/image/qpixmap_s60.cpp

Reviewed-by: Jason Barron