Flying portal balls now spawn a few spark effects
This has been adapted from PortalEffects from HedgeEditor.
HedgeEditor already included such effects for some reason, so they have been removed as redundant.
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