- Add WEBPMUX support back to WebPDecode_wrapper (to support older versions of libwebp that have mux support, but not animation)
- Add HAVE_WEBPANIM flag, and use it appropriately
- Update documentation / tests
- Support writing metadata chunks with WebPAnimEncoder
- Add XMP metadata support to legacy WebPEncode wrapper
- Cleanup unused mux code in legacy WebPDecode wrapper
- Fix some bugs present when compiled without WebP Mux support
- Fix conversion from L/P/PA modes when saving WebP files
- Update existing tests, and add new ones for WebP animation and metadata support