Strip invalid PNG profiles from PNGs
Bad PNGs caused a few annoying warnings like “libpng warning: iCCP: known incorrect sRGB profile”.
Command used:
pngcrush -rem gAMA -rem cHRM -rem iCCP -rem sRGB
Note that many images have “@2x” in their name, this probably explains why they have been overlooked before.
07f3bf8d98a3
Hedgewars.png had a resolution more than twice as high as required; also fixed some (mostly obsolete) code that also contained a typo that would cause a warning/note in clang
