Add ff_ prefix to data symbols of encoders, decoders, hwaccel, parsers, bsf.

None of these symbols should be accessed directly, so declare them as
hidden.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit d36beb3f69)

libavcodec/aac_parser.c

@@ -60,7 +60,7 @@ static av_cold int aac_parse_init(AVCodecParserContext *s1)
 }
 
 
-AVCodecParser aac_parser = {
+AVCodecParser ff_aac_parser = {
     { CODEC_ID_AAC },
     sizeof(AACAC3ParseContext),
     aac_parse_init,