Add G_SLICE=debug-blocks to test environment
Fix check for errors when writing WavPack tags
Add -Werror=return-type to compiler flags
Use a stack-allocated buffer for WavPack tags
Support album artist in WavPack tags
Clear empty tag fields when saving WavPack tags

Refactor WavPack tag saving to use a new
et_wavpack_append_or_delete_tag_item() helper function. Call
WavpackDeleteTagItem() to delete a tag item if the item is empty.
Fix string leak when reading WavPack tags