decoder/{opus,vorbis}: support embedded pictures (METADATA_BLOCK_PICTURE)

More for https://github.com/MusicPlayerDaemon/MPD/issues/42

src/decoder/plugins/OpusTags.cxx

@@ -19,6 +19,7 @@
 
 #include "OpusTags.hxx"
 #include "OpusReader.hxx"
+#include "lib/xiph/VorbisPicture.hxx"
 #include "lib/xiph/XiphTags.hxx"
 #include "tag/Handler.hxx"
 #include "tag/ParseName.hxx"
@@ -45,6 +46,10 @@ ScanOneOpusTag(StringView name, StringView value,
 	       ReplayGainInfo *rgi,
 	       TagHandler &handler) noexcept
 {
+	if (handler.WantPicture() &&
+	    name.EqualsIgnoreCase("METADATA_BLOCK_PICTURE"))
+		return ScanVorbisPicture(value, handler);
+
 	if (value.size >= 4096)
 		/* ignore large values */
 		return;

src/decoder/plugins/meson.build

@@ -192,6 +192,7 @@ decoder_plugins = static_library(
 decoder_plugins_dep = declare_dependency(
   link_with: decoder_plugins,
   dependencies: [
+    crypto_base64_dep,
     decoder_api_dep,
     pcm_dep,
   ],