AngryBirds 1.5.3.0.0 fix window reuse from "preserve aspect" to full-fledged and add new setting in the ini file.

fix window reuse from "preserve aspect" to full-fledged (fixed by Bargmy) and add new setting in the ini file:

Keep running when inactive

By default the game pauses when its window loses focus (original behavior).
To keep it running while Alt-Tabbed (e.g. no freeze when switching to
another app), set in AngryBirds.ini:
[Window]
KeepRunningInBackground=1 (by default = 0 with original behavior).

Several minor fixes.