Remove m_glContextInitialized, simplify updateScreen

[mcarans]

@phkb @LW-archlinux If this works but not #726, then I'll merge this otherwise I'll merge 726 instead as it is a superset of this.

[mcarans]

Setting to draft while I investigate failure on master

[mcarans]

@phkb @LW-archlinux I have rebased this with the fix (the revert) merged into master. Please let me know if it works for you.

[mcarans]

@oocube I saw you're commenting again. Please can you check this PR works for you. If this works but not #726, then I'll merge this otherwise I'll merge 726 instead as it is a superset of this.

The flatpak failure is that the archive.mesa3d.org site used by a dependency that FlatHub demanded is temporarily down so please ignore for now. Flatpak build working now

[LW-archlinux]

Both #725 and #726 work fine.

[oocube]

I downloaded and tested Oolite-1.93.1-PullRequest725.3137-dev-x86_64.AppImage. While checking for the same things I did on the #726 build actually I could not make out any difference.

Oolite-1.93.1-PullRequest725.3137-dev-x86_64.AppImage runs well - I did not observe any problems. Positioning and resizing is smooth.

I also checked the fullscreen option, and switching it on and off does not cause any delays for me.
Just as before I was curious where the fullscreen window goes, but apparently the game gets fullscreen on the screen it is running on when I turn on fullscreen. Absolutely ok for me.

Then I was wondering about the offered resolutions. I have two full HD screens (1920x1080) and one smaller (1680x1050) as the main screen. Oolite offers only resolutions fit for the smaller monitor, even if it runs on the other one. But it did not feel like this setting has any effect. Should it?

[mcarans]

Closing this in favour of #726 which is a superset