remove common macros used in the span functions of most drivers from the individual...

remove common macros used in the span functions of most drivers from the individual drivers and put them in common code. It is still possible for a driver to define its own macros if it has special needs. This affects CLIPPIXEL, CLIPSPAN, HW_CLIPLOOP, HW_ENDCLIPLOOP, and for drivers using the spantmp2 template also GET_SRC_PTR and GET_DST_PTR.