Revert "lavf/concatdec: define "ffcat" and "ffconcat" extensions"

This reverts commit 6cc12353a8.

Conflicts:
	libavformat/version.h

Allowing to automatically select the concat demuxer raises
security concerns, as it allows a possibly hostile file to
access any file on the system. Guessing the format based on
the file name extension does not allow to enable the safe
mode designed to avoid it.

libavformat/concatdec.c

@@ -289,5 +289,4 @@ AVInputFormat ff_concat_demuxer = {
     .read_packet    = concat_read_packet,
     .read_close     = concat_read_close,
     .priv_class     = &concat_class,
-    .extensions     = "ffconcat,ffcat",
 };

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 54
 #define LIBAVFORMAT_VERSION_MINOR 63
-#define LIBAVFORMAT_VERSION_MICRO 102
+#define LIBAVFORMAT_VERSION_MICRO 103
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \