Update librsync.spec for release v2.3.1.
Update librsync.spec for release v2.3.1.

dbaarda/librsync,librsync/librsync,dbaarda/librsync,sourcefrog/librsync,sourcefrog/librsync,dbaarda/librsync,librsync/librsync,librsync/librsync,dbaarda/librsync,librsync/librsync,sourcefrog/librsync,sourcefrog/librsync