Make mpg123 optional
Unfortunately due to patent/legal reasons, not everyone has access to mpg123. I'm actually trying to get LOVE into Fedora but it can't be included with mpg123, as it's not included in Fedora and patent/legal reasons go against Fedora guidelines.
Fortunately, someone at openSUSE made a patch to make it optional. The webpage I got it from doesn't seem to exist anymore but fortunately I save it to my computer. I attached the patch in hopes it gets included into LOVE.