Gamma correction workaround

[Karagy]

This "bug" stably is reproduced in Windows (XP) in window mode (not fullscreen).
When gamma correction is exposed not in 100, for example in 200, it is possible to observe the following effect:
- when focus at Tome window - brightness of a desktop so increases - ok, no trouble.
- when focus out Tome window - brightness of a desctop (and Tome window) revert to normal - ok, no trouble.
- but when You exit Tome - brightness of a desktop remains raised - very inconveniently.

I didn't study source code TOME, but if there there is a gamma correction handling at focus loss, it makes sense to add such on exit from application.