Shader: Group all shaders in one collective struct

Makes sharedstate.{cpp|h} a lot easier to read, and
adding new shaders a one liner.
Graphics: Fix some RGSS2 bitrot
Audio: Silence "unused" errors with latest libvorbisfile
Remove unneeded include
Audio: Prevent div-by-zero
MRI-Binding: Fix typo that led to access of freed Color objects

Also fix my moronic variable naming in the InitCopy
functions that let to this mess up in the first place.
FileSystem: Add "otf" to recognized font extensions