Adds muzzle flash to all vehicles and ships with cannons.

Muzzle animation is a customized version of the original gunfire.shp. Not using all frames for light tank, flak truck and flak cannon is intentional.
Apply GTWR fix to RA defenses (pillboxes, flame turret) as well.
Set/fix LocalOffsets for all units and structures with muzzle flashes in RA mod.

Offsets that haven't been touched were either forgotten or deemed good enough.
Merge pull request #3639 from reaperrr/muzzles

Offsets and muzzle flashes