e hooks for
initializing and tearing down mappings at the right times.  Testing involved at
least starting X, running glxgears, killing glxgears, exiting X, and repeating.

Tested on:      FreeBSD (g200, g400, r200, r128)
                Linux (r200, savage4)

From: Eric Anholt <anholt@freebsd.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>
I.”óž