mesa: handle GL_UNSIGNED_INT64_ARB properly (v2)

Bindless texture handles can be passed via vertex attribs using this type.
This fixes a bunch of bindless piglit tests on radeonsi.

Cc: 18.0 18.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
(cherry picked from commit a8e14138)
[Juan A. Suarez: resolve trivial conflict]
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>

Conflicts:
	src/mesa/vbo/vbo_private.h