Attribute roll animation takes a strangely long time

[RMTEW FULL NAME]

The code was the same as for Allegro, but.. who knows.

Now the animation has been adjusted to only display for 0.5 seconds per attribute.

[RMTEW FULL NAME]

The attribute rolling animation took a strangely long time. The animation display update, and display delay were the same, but just seemed more effective (and slower) under libtcod. This is fixed by only updating the animation for the first 0.5 seconds of the roll, as it's all a super fast graphical affectation anyway. Fixes #202

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