Linux Painting Invalidation broken 8.0.1 to 8.0.2 due to Component::isShowing changes

[reuk]

This is now fixed on develop:

Component::isShowing broken in Ableton Live

Thanks for reporting, we’ve reverted the majority of the initial change to restore the correct behaviour of OpenGL components: The ComponentPeer::isShowing function is still in place, so it is still possible to determine whether a component is displayed on-screen by calling this function on the current peer.