Attempt to fix buffer overflows with rDNS tags

[ocococococ]

As asked,
I created this PR with a test_reverseDNS.sh script to test adding many rDNS tags to already provided issue-32.mp4.

Without this patch, there are still buffer overflows.
Corresponding ASAN report is already uploaded here: #62

[ocococococ]

FYI, as I am mostly a Mac user, and with latest commit, binary output of rDNS tags appears identical to
those generated by tools like Subler or Musicbrainz Picard.
Moreover, It also seems ok with freyr-js regarding these comments before replacing AtomicParsley by lofty-rs.
Finally, I managed to check that even under Windows, it seems to work too.

[miraclx]

Checks out! Thanks! 💪🏽

[howyallare]

I think this was right the first time being initialised to 12. Otherwise you can get a buffer overrun and an invalid "name" atom written to file when the length of its value is 16.

[ocococococ]

Tried with value 12 instead of 16 on a single file and indeed it seems to work.

[ghjimmy]

Without this patch AtomicParsley on Apple Silicon native corrupts files when using --rDNSatom

% sh redo
Before and after tagging with /tmp/AtomicParsley.brew
197632 -rw-r--r--@ 1 jimmy  staff  93658182  8 Jun 09:37 movie.mp4
4196048 -rw-r--r--@ 1 jimmy  staff  2148376318  8 Jun 09:37 movie.mp4
Before and after tagging with /tmp/AtomicParsley.arm
182928 -rw-r--r--@ 1 jimmy  staff  93658182  8 Jun 09:37 movie.mp4
182664 -rw-r--r--@ 1 jimmy  staff  93521292  8 Jun 09:37 movie.mp4
% cat redo
AP1=/tmp/AtomicParsley.brew
AP2=/tmp/AtomicParsley.arm
f=movie.mp4
for AP in "$AP1" "$AP2"
do
    cp /tmp/$f .
    echo Before and after tagging with $AP
    ls -sl $f
    $AP "$f" --overWrite --metaEnema --artwork REMOVE_ALL  \
--rDNSatom "<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE plist PUBLIC '-//Apple//DTD PLIST 1.0//EN' 'http://www.apple.com/DTDs/PropertyList-1.0.dtd'>
<plist version='1.0'>
<dict>
	<key>cast</key>
	<array>
		<dict>
			<key>name</key>
			<string>Peter Pepper</string>
		</dict>
	</array>
</dict>
</plist>" name="iTun" domain="com.apple.iTunes" \
--stik 'Movie' \
--title 'Diamond' \
--year '2010-03-18-T12:00:00Z' --freefree >/dev/null 2>&1
    ls -sl $f
done

[wez]

Resolved by #71