gallium: add a flag to turn on gl rasterization rules

Use this to set up hardware rasterization (if your hardware can
do it) or otherwise turn on various tweaks in the draw module.

Currently only hooked up to point biasing code.

src/mesa/state_tracker/st_atom_rasterizer.c

@@ -261,6 +261,8 @@ static void update_raster_state( struct st_context *st )
    if (ctx->Scissor.Enabled)
       raster->scissor = 1;
 
+   raster->gl_rasterization_rules = 1;
+
    cso_set_rasterizer(st->cso_context, raster);
 }