mkvtoolnix: remove 'header compression' for mkvmerge on old releases (>= 4.2.0 and below 6.x ?)

Some mkvtoolnix tweaks

# The mkvtoolnix version that can be used on ARMv5 devices is an old 4.2.0-1 release.
# In this release, default is to switch on 'header compression'

# The solution is to take all tracks from a compressed file and have the corresponding headers uncompressed with the `--compression -1:none` (-1 is a wildcard for 'all tracks')

# This flag must be used for each input file, e.g.

mkvmerge -o "output.mkv" --compression -1:none "input1.mp4" --compression -1:none "input2.ac3"  ...

# So, for adding subs.srt in an already existing mkv:
mkvmerge -o "output.mkv" --compression -1:none "input1.mkv" --language 0:eng --track-name 0:English subs.srt

# To know current charset
file -I *.srt

# If charset change is needed
iconf -f fromcode -t tocode in.srt > out.srt


# Batch add srt files, assuming same filename for file and episode (+bonus: using mp4 -> mkv)
for i in `ls *.mp4`; do mkvmerge -o mkv/${i:0:${#i}-3}mkv --compression -1:none $i --language 0:eng --track-name 0:English Subs/${i:0:${#i}-3}srt; done