Invalidate render state tracking of current texture binding (#784)
Invalidate render state tracking of current texture binding (#784)

- When texture unit is changed, the current texture binding should be invalidated #777
quitejonny/tangram-es,cleeus/tangram-es,tangrams/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,tangrams/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,tangrams/tangram-es,cleeus/tangram-es,cleeus/tangram-es