i965: Store the command parser version number in intel_screen

i965: Store the command parser version number in intel_screen

In order to detect whether the predicate source registers can be used
in a later patch we will need to know the version number for the
command parser. This patch just adds a member to intel_screen and does
an ioctl to get the version.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>