Add magic for Musepack SV8
According to http://trac.musepack.net/musepack/wiki/SV8Specification , the file starts with a 'MPCK' magic.
Currently, only the SV7 (http://trac.musepack.net/musepack/wiki/SV7Specification) magic, 'MP+' is recognized.
According to http://trac.musepack.net/musepack/wiki/SV8Specification , the file starts with a 'MPCK' magic.
Currently, only the SV7 (http://trac.musepack.net/musepack/wiki/SV7Specification) magic, 'MP+' is recognized.