asfdec: also read Metadata Library Object

In some ASF files this objects holds cover art and other tags. Compared to
Metadata Object it can also hold GUIDs, but we ignore these for now.

Signed-off-by: Vladimir Pantelic <vladoman@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/asf.c

@@ -109,6 +109,10 @@ const ff_asf_guid ff_asf_metadata_header = {
     0xea, 0xcb, 0xf8, 0xc5, 0xaf, 0x5b, 0x77, 0x48, 0x84, 0x67, 0xaa, 0x8c, 0x44, 0xfa, 0x4c, 0xca
 };
 
+const ff_asf_guid ff_asf_metadata_library_header = {
+    0x94, 0x1c, 0x23, 0x44, 0x98, 0x94, 0xd1, 0x49, 0xa1, 0x41, 0x1d, 0x13, 0x4e, 0x45, 0x70, 0x54
+};
+
 const ff_asf_guid ff_asf_marker_header = {
     0x01, 0xCD, 0x87, 0xF4, 0x51, 0xA9, 0xCF, 0x11, 0x8E, 0xE6, 0x00, 0xC0, 0x0C, 0x20, 0x53, 0x65
 };