around CPU access to the framebuffer. This allows the hardware to set
up swappers to deal with endianness, or to tell EXA to move the pixmap
out to framebuffer if insufficient swappers are available (note: must
not fail on front buffer!).
Submitted by: benh
simplify/clarify it for driver writers who probably don't want to know
what pPixmap->devPrivate.ptr or pPixmap->devKind mean. Converts the sis
driver to use them, and bumps the EXA module minor version.