sega/model2: apply color table to tilemap layers; indy500 supports 16:9

[gm-matthew]

Applying the color table to tilemap layers results in Behind Enemy Lines correctly fading to/from black when starting a game. It is necessary to refresh the whole palette if the scroll (tilemap) color table is written to.

I assume that the scroll color table is used when direct framebuffer drawing is enabled, since pixels are in 15-bit RGB format without a luminance component.

Indy 500 deluxe cabinets use 16:9 monitors:

Also the CRTC offset values when drawing directly to the framebuffer have been corrected; the title screen of Last Bronx now appears exactly in the correct position.

I'm debating whether to remove the fixed gamma adjustment in favor of letting the user use the brightness/contrast sliders, since the "gamma curve" varies from game to game, however this would lead to some games looking very washed out before adjustment and users who are unaware of the slider settings might be unhappy with the change. I don't think it is possible to apply custom brightness/contrast values in the driver itself (if there is a way, I'd be delighting to hear it).

We could perhaps use PORT_ADJUSTER to add sliders that allow users to adjust the "gamma curve" while applying settings that look decent for most games out of the box.