Remove unnecessary <sys/malloc.h>.

add counter to periodically drain the instruction queue in order to avoid
stalling the MBus during long SX operations
adapted from xf86-video-suncg14

initialize the diagnostic register with the value suggested by the SunOS
header. This sets a bunch of undocumented bits and yields a 10% speed increase
when rendering antialiased text.

Add missing double p and d for stopped and overriden accordingly.
Fix few more typos along the way, mainly in copy-pasted comments.

adapt to changes in sxreg.h

print chip revision on attach

fix typos, deal with hardware insanity

attachment and initialization for SX