gallium: add a index argument to create_query

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
gallium: add a cap for max vertex streams

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
mesa/st: add vertex stream support

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: fix emitting vertex stream

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: avoid creating restarts with non-0 stream

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: only merge emit/restart for identical streams

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0: expose 4 vertex streams, use stream ids in xfb

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>