comment.c: fix duplicates detection logic in comments_add()

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
id3: allow 3-character frame IDs

This is sometimes encountered in the wild.

Bump cache version to force tags re-reading.

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
ReplayGain: default to peak of 1

Following spec:
http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_specification#Clipping_prevention

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
ReplayGain: default to pre-amp gain of 0

Following spec:
http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_specification#Pre-amplification

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
ape: read APE tags at the end of file but before ID3v1 one in fast mode

Otherwise, we ignore valid APE tags in MP3 files which might contain e.g. ReplayGain data.

Bump cache version to force tags re-reading.

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>