Properly fixed text/graphics mode of the S3 pre-ViRGE cards.
PIX TRANS cleanups.
Added a sanity check to banking, per bit 0 of CRTC31.
Initial implementation of Enhanced 4-bit mode.
911/924 chips use CRTC43 bit 3 for enabling 15/16bpp mode.
fb_only variable used correctly as of now (depending if on 4bit or 8bit+ modes).
S3 ViRGE changes part 2:
Made the Trio3D/2X AGP use the PCI_ADD_AGP part accordingly
RAMDAC changes:
Sierra 11483 and 11487 don't have an RS2 signal so the four times reading scheme of 0x3c6 is used instead, per documentation.
Fixed AT&T 49x bpp selection.
Other changes:
Fixed remaining rendering issues with the Radius SVGA HT209 card.