llvmpipe: handle more queries

llvmpipe: handle more queries

Handle PIPE_QUERY_GPU_FINISHED and PIPE_QUERY_TIMESTAMP_DISJOINT, and
also fill out the ps_invocations and c_primitives from the
PIPE_QUERY_PIPELINE_STATISTICS (the others in there should already
be handled). Note that ps_invocations isn't pixel exact, just 16 pixel
exact but I guess it's better than nothing.
Doesn't really seem to work correctly but there's probably bugs elsewhere.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>