fix: Use replaygain tags for .m4a type family files too, closes Ticket #13948 

Log file extract after pach applied:

13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]: Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/userx/shared/Archive/recit16bit.m4a':
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:   Metadata:
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     major_brand     : mp42
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     minor_version   : 0
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     compatible_brands: M4A mp42isom
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     creation_time   : 2013-01-10 20:23:34
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     track           : 2/2
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     title           : Example Trac AAC
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     encoder         : Nero AAC codec / 1.5.4.0
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:   Duration: 00:00:09.08, start: 0.000000, bitrate: 243 kb/s
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     Chapter #0.0: start 0.059501, end 9.079000
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     Metadata:
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:       title           : Example Trac AAC
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 240 kb/s
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:     Metadata:
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:       creation_time   : 2013-01-10 20:23:34
13:04:48 T:140262136039296    INFO: ffmpeg[52CB4780]:       handler_name    : Sound Media Handler
13:04:48 T:140262136039296   DEBUG: CDVDDemuxFFmpeg::AddStream(0, ...) -> 0
13:04:48 T:140262136039296   DEBUG: FactoryCodec - Audio: passthrough - Opening
13:04:48 T:140262136039296   DEBUG: FactoryCodec - Audio: passthrough - Failed
13:04:48 T:140262136039296   DEBUG: FactoryCodec - Audio: FFmpeg - Opening
13:04:48 T:140262136039296   DEBUG: FactoryCodec - Audio: FFmpeg - Opened
13:04:48 T:140262136039296    INFO: AudioDecoder: File is queued
13:04:48 T:140262136039296   DEBUG: AudioDecoder::GetReplayGain - Final Replaygain applied: 1.823896, Track/Album Gain 94.220001, Peak 0.320437