vrend: queries should be fenced and use guest pages
The first two commits make queries fenced. That is, the result of a query is available after a fence after the query is waited for.
The last three commits change PIPE_BIND_CUSTOM buffers to use guest pages, by removing the intermediate buffer pointed to by res->ptr.
Together with mesa/mesa!487 (merged), TF2 goes from 17fps to 40fps.
Edited by Chia-I Wu