avcodec: add a cook parser to get subpacket duration

Fixes jittery video playback of rm files with cook audio.

libavcodec/allcodecs.c

@@ -400,6 +400,7 @@ void avcodec_register_all(void)
     REGISTER_PARSER  (AC3, ac3);
     REGISTER_PARSER  (ADX, adx);
     REGISTER_PARSER  (CAVSVIDEO, cavsvideo);
+    REGISTER_PARSER  (COOK, cook);
     REGISTER_PARSER  (DCA, dca);
     REGISTER_PARSER  (DIRAC, dirac);
     REGISTER_PARSER  (DNXHD, dnxhd);