remove use of implicit variables from pushbuf macros

remove use of implicit variables from pushbuf macros

This matches the gallium winsys now.  At some point the ddx will get updates
so the "common" code is once again in sync to make it easier to do mm
changes to both the ddx and dri simultaneously.

But, I want to get this part out of the way first as the changes might take
a bit of work - and I don't want to have to deal with merge conflicts
everywhere if someone changes the accel code before I'm done :)