SvxBackgroundTabPage::FillItemSet: handle XFILL_GRADIENT -> XFILL_SOLID
SvxBackgroundTabPage::FillItemSet: handle XFILL_GRADIENT -> XFILL_SOLID

This makes it possible to turn off the gradient background of a Writer
frame.

Change-Id: Ic7bdfec252847f463da47c838c7de0fdb7625869

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core