pageflipping after a mode switch
take current page into account in AdjustFrame(); writing the CRTC offset
via the CP was probably a bad idea as this can happen asynchronously,
reverted
take frame offset into account when flipping pages
handle CRTC2 as well for pageflipping (untested)
preserve GEN_INT_CNTL on mode switches to prevent interrupts from getting
disabled
ioctl. The DRM reads them from memory addresses the chip writes to on
updates. Fall back to reading the registers directly with an old DRM.
(Tim Smith, cleanups by myself)