fix minor bug in wvgain where the -q (quiet) option would cause the -c (clean) option to fail reporting no ReplayGain tags found
add read-only access to APEv2 tags that come at the beginning of WavPack files - these were never intended, but they exist in the wild and this will allow them to be somewhat handled (at least well enough for transcoding) - a few changes to make sure we do not attempt to edit such tags (for obvious reasons), and properly inform the user if attempted (with wvgain, for example) - also fix a -Wall warning for unused variable assignment