Remove some unused private data members.
Remove some unused private data members.

Distrotech/taglib,black78/taglib,black78/taglib,black78/taglib,taglib/taglib,taglib/taglib,TsudaKageyu/taglib,TsudaKageyu/taglib,Distrotech/taglib,TsudaKageyu/taglib,Distrotech/taglib,taglib/taglib