Avatars: better filtering

[MairusuPawa]

USDX WP b2 introduced a new feature, avatars representing the player. They turned out to be quite popular when tested at a convention.

Unfortunately, they look weird in-game: pixelation (point filtering?) + deformed aspect ratio (widescreen). Would it be possible to handle them which a better filtering algorithm at least?

[basisbit]

this will need some work because currently, the avatar images are done as buttons and the current button code only does good up-scaling of images but no down-scaling, so opengl uses point-filtering.