two more screen functions need to be queue funtions so that operations properly synced

[skibu]

This issue is very similar to PR #1795 . I found two more screen drawing functions that need to be queue functions so that all the drawing functions are executed in the proper order. Otherwise drawing can end up with completely incorrect results.

Tagging @tlubke since they were the one who properly fixed the similar issues in PR #1795 .

The functions that need to be made into queue functions are:

• image:_context_focus()
• image:_context_defocus()

For more info on the problem and how I added a hack to normsLib to get around it, see: https://github.com/skibu/nornsLib/blob/eecaba928f5972363c75087cbb407d09efb7092c/screenExt.lua#L142

[tlubke]

I actually had some work done in this area already if you want to checkout
f2f8eb6 on tlubke/#1808. I think every screen function called by image:_context_focus() and image:_context_defocus() now has a proper event in that branch.

It's not quite PR-ready though. After looking over it just once, I found that SCREEN_RESULTS_SURFACE_GET_EXTENTS is not handled in the switch statement inside screen_results_free().

[Dewb]

related: #1747