Cherry-pick non-Xorg-1.20-specific fixes from xorg-server dir.

Use proper ANSI offsetof(3) to specify framebuffer offset in struct.
Add prototype declarations for CG2 functions.
Implement functions to restore palette settings on exiting Xserver.
Explicitly initialize origColormapValid for readability.
Fix LED defintions to match xkb/xkbInit.c.
Remove unused functions required to handle non-XKB autorepeat.
Initialize ModMap dynamically using keymap data per each keyboard.
Remove now unused ModMap data for each keyboard.
Use "empty" for rmlvo model and layout to avoid lingering default settings.
Trailing whitespace.

Note it looks there is some serious performance regression
between Xorg 1.10 and 1.20 on rendering root_weave to root window
on 3/60 bwtwo mono server.

(tsutsui)