Changed the color of the "SPKRA0" sprite to orange and made it low-res to fit...

This replaces the voice chat's speaker icon(s), from salmon-coloured to orange a la GoldSrc engine, and making it low-res so that it fits better with Doom's aesthetics. I wasn't too happy with the hi-res version that originates from (G)ZDoom that had to be scaled down and offset via TEXTURES to make it fit. Here are the before and after images respectively:

Note that this modifies the SPKRA0 sprite that comes from (G)ZDoom. This sprite isn't used for anything, and AFAIK isn't used in GZDoom nowadays either, but I still added a history entry to mention that it has been changed.