version in the licensing statement does not get altered mistakenly.
- Fixed GPL version number in alertsound plugin from v4 back to the
original v2.
r8961 (2015) mistakenly changed it from v3 to v4
r7728 (2011) mistakenly changed it from v2 to v3
- obfuscated the GPL version number, abbreviating "version" and
using creative math with some paretheses to prevent future,
unintended changes to the license statement's version.
