riff: recognize upper-case "ID3" chunk name

Some tagging libraries (eg. TagLib) produce that variant.

NEWS

@@ -1,6 +1,8 @@
 ver 0.18.6 (not yet released)
 * input
   - cdio_paranoia: support libcdio-paranoia 0.90
+* tags
+  - riff: recognize upper-case "ID3" chunk name
 * output
   - openal: fix build failure on Mac OS X
   - osx: fix build failure

src/tag/Riff.cxx

@@ -87,7 +87,8 @@ riff_seek_id3(FILE *file)
 			/* pad byte */
 			++size;
 
-		if (memcmp(chunk.id, "id3 ", 4) == 0)
+		if (memcmp(chunk.id, "id3 ", 4) == 0 ||
+		    memcmp(chunk.id, "ID3 ", 4) == 0)
 			/* found it! */
 			return size;