Needs test: Secondary and Third Alternative Tool no longer reset to the first tool if you let go of the button

[SirVer]

The bug has been fixed, but we still want a test.

SHIFT(hold): selects first alternative tool while pressing
ALT(hold): Selects second alternative tool while pressing

Holding the key do not work as described. You could release the key but the tool doesn't change to its normal state.

I.e.: In case of height tool, pressing shift will leave the tool to decrease height. You have to click on height tool again to get its normal state (increase height).

[SirVer (sirver)]

This regressed twice already. time to add a test.

[GunChleoc (gunchleoc)]

While working on something else, I noticed that the SDL_KEYUP event isn't being handled, which is at the root of the problem. So, I made a quick branch. Not compiled or tested; so this bug is is still up for grabs until I get around to it.

[GunChleoc (gunchleoc)]

OK, compiled and tested. This was indeed the problem, so I have made a merge request.

We still need to write a test for this though. I'll be happy to do so if somebody teaches me how.

[GunChleoc (gunchleoc)]

Migrated to https://github.com/widelands/widelands/issues/965