winsys/svga: Replace the query mm buffer pool with a slab pool v3

winsys/svga: Replace the query mm buffer pool with a slab pool v3

This is to avoid running out of query buffer space due to winsys
limitations. Instead of a fixed size per screen pool of query buffers,
use a slab allocator that allocates a new slab if we run out of space
in the first one.

v2: Correct email addresses.
v3: s/8192/VMW_QUERY_POOL_SIZE/. Improve documentation and log message.

Reported-and-tested-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Cc: "10.1" <mesa-stable@lists.freedesktop.org>