lavf/apngenc: Fix png remuxing by using default extension apng.

Changelog

@@ -12,7 +12,7 @@ version <next>:
 - Detelecine filter
 - Intel QSV-accelerated H.264 encoding
 - MMAL-accelerated H.264 decoding
-- basic APNG encoder and muxer
+- basic APNG encoder and muxer with default extension "apng"
 - unpack DivX-style packed B-frames in MPEG-4 bitstream filter
 - WebM Live Chunk Muxer
 - nvenc level and tier options

libavformat/apngenc.c

@@ -259,7 +259,7 @@ AVOutputFormat ff_apng_muxer = {
     .name           = "apng",
     .long_name      = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
     .mime_type      = "image/png",
-    .extensions     = "png",
+    .extensions     = "apng",
     .priv_data_size = sizeof(APNGMuxContext),
     .audio_codec    = AV_CODEC_ID_NONE,
     .video_codec    = AV_CODEC_ID_APNG,

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 56
 #define LIBAVFORMAT_VERSION_MINOR  31
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MICRO 102
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \