Various characters don't work in program editor

[krzys-h]

Confirmed for:
ÖÄÜöäüß
ąćęńśżź

Seems to work fine if you paste them from a text editor.

[twothe]

Related to this: you cannot type any of the following important characters on a German keyboard, because the AltGr key is not recognized: { } [ ]
This makes it basically impossible to play the game.

In addition German characters (öäüß) are not properly displayed.

[krzys-h]

@twothe This one should be fixed in the next release thanks to SDL2 migration (see dev branch in the repo or http://compiled.colobot.info/jenkins/view/colobot-gold-download/ for prelease builds)
The main problem in this issue is the multi-byte encoding of some of those characters, the Ui::CEdit class currently doesn't support inserting those too well.

[twothe]

Confirmed: AltGr issue is fixed on the latest dev version.

[B-CE]

Related to #1003 and PR #1116