SwXPageStyle: make sure SHARED_FIRST is added to both HEADER and FOOTER sets
SwXPageStyle: make sure SHARED_FIRST is added to both HEADER and FOOTER sets

It makes no sense to alter only the header set, as this property affects
both.

Change-Id: I7a34f97d144f877f808506e6ed961745994bb9a1

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