Nif loader: workaround for missed textures in BB/BH

Works for Better Bodies / Better Heads addons.
Updated credits.txt and corrected license info in readme.txt
properly handle potentially non 16 bit planar audio formats
Support float samples with ffmpeg

Requires the AL_EXT_FLOAT32 extension in OpenAL
Merge remote-tracking branch 'zini/master' into misc-cleanup
Forgot the release manager and added the license terms of EB Garamond
Merge remote-tracking branch 'pvdk/credits2'
Merge remote-tracking branch 'sergeyshambir/BBfix'