avcodec/pngdec: add APNG support.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/allcodecs.c

@@ -105,6 +105,7 @@ void avcodec_register_all(void)
     REGISTER_ENCDEC (AMV,               amv);
     REGISTER_DECODER(ANM,               anm);
     REGISTER_DECODER(ANSI,              ansi);
+    REGISTER_DECODER(APNG,              apng);
     REGISTER_ENCDEC (ASV1,              asv1);
     REGISTER_ENCDEC (ASV2,              asv2);
     REGISTER_DECODER(AURA,              aura);