gallium: add caps for MIN/MAX texel offsets.

As per Brian's suggestion, add caps for drivers that support texture
offsets to advertise a min/max via TGSI, also use it in the state tracker.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_extensions.c

@@ -203,6 +203,9 @@ void st_init_limits(struct st_context *st)
 
    /* XXX we'll need a better query here someday */
    if (screen->get_param(screen, PIPE_CAP_GLSL)) {
+      c->MinProgramTexelOffset = screen->get_param(screen, PIPE_CAP_MIN_TEXEL_OFFSET);
+      c->MaxProgramTexelOffset = screen->get_param(screen, PIPE_CAP_MAX_TEXEL_OFFSET);
+
       c->GLSLVersion = 120;
    }
 }