Corrected GetDrawBackgrdColor to return a value, not a reference

(cherry picked from commit a8a2653568d31a2fb76aeb3183e128e3304452bd)

Conflicts:
	sw/source/core/layout/paintfrm.cxx

Change-Id: I1e0a5a255d67d130f85a8c5c739c4e5cd4ce03c5