svx: always set SharedFirst to True for now in SvxHFPage::FillItemSet()
svx: always set SharedFirst to True for now in SvxHFPage::FillItemSet()

This feature is not complete yet (so adding real UI doesn't make sense
yet), but the lack of SID_ATTR_PAGE_SHARED_FIRST caused a crash in sw's
ItemSetToPageDesc().

Change-Id: I3832b617aba50ad7d451766628bbb005879d25fe

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