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.
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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.