Beta 4

Fixes

• the dreadful "lost stream sync" error is gone
• shadows are rendered again if the floor is far away from the shadow caster
• some static meshes are invisible now as they are intended to

New Features

• water has a new specular component which makes it look a bit more "classic"

Improvements

• libsndfile has been completely removed and replaced with ffmpeg because of some issues with audio handling
• same with glew, which is replaced by glad now
• shader handling was a bit simplified