apng: Add a basic APNG muxer

Additionally, update some documentation with support for APNG
Signed-off-by: Donny Yang <work@kota.moe>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -12,6 +12,7 @@ version <next>:
 - Detelecine filter
 - Intel QSV-accelerated H.264 encoding
 - MMAL-accelerated H.264 decoding
+- basic APNG encoder and muxer
 
 
 version 2.6:

doc/general.texi

@@ -222,6 +222,7 @@ library:
     @tab Audio format used on the Nintendo Gamecube.
 @item AFC                       @tab   @tab X
     @tab Audio format used on the Nintendo Gamecube.
+@item APNG                      @tab X @tab X
 @item ASF                       @tab X @tab X
 @item AST                       @tab X @tab X
     @tab Audio format used on the Nintendo Wii.
@@ -508,6 +509,7 @@ following image formats are supported:
 @item Alias PIX    @tab X @tab X
     @tab Alias/Wavefront PIX image format
 @item animated GIF @tab X @tab X
+@item APNG         @tab X @tab X
 @item BMP          @tab X @tab X
     @tab Microsoft BMP image
 @item BRender PIX  @tab   @tab X

libavformat/Makefile

@@ -80,6 +80,7 @@ OBJS-$(CONFIG_ANM_DEMUXER)               += anm.o
 OBJS-$(CONFIG_APC_DEMUXER)               += apc.o
 OBJS-$(CONFIG_APE_DEMUXER)               += ape.o apetag.o img2.o
 OBJS-$(CONFIG_APNG_DEMUXER)              += apngdec.o
+OBJS-$(CONFIG_APNG_MUXER)                += apngenc.o
 OBJS-$(CONFIG_AQTITLE_DEMUXER)           += aqtitledec.o subtitles.o
 OBJS-$(CONFIG_ASF_DEMUXER)               += asfdec.o asf.o asfcrypt.o \
                                             avlanguage.o

libavformat/allformats.c

@@ -74,7 +74,7 @@ void av_register_all(void)
     REGISTER_DEMUXER (ANM,              anm);
     REGISTER_DEMUXER (APC,              apc);
     REGISTER_DEMUXER (APE,              ape);
-    REGISTER_DEMUXER (APNG,             apng);
+    REGISTER_MUXDEMUX(APNG,             apng);
     REGISTER_DEMUXER (AQTITLE,          aqtitle);
     REGISTER_MUXDEMUX(ASF,              asf);
     REGISTER_MUXDEMUX(ASS,              ass);