Update and change license information of Droplet sounds, now it's CC BY 3.0
Was previously labelled under license CC Sampling+ 1.0, which is
considered non-free by FSF, OSI and DFSG.
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
