[tz] version information in tz binary file?

[Paul Eggert]

One other thing.  It's been privately suggested to me,
more than once, that a tz binary file should have
a version number in it, identifying which version of
the tz data it came from.  Presumably this could be
a new option to 'zic', used by Makefile, e.g.,

   zic -V "$(VERSION)" ...

would copy the value of VERSION into the zic output file.

Do you think this is a good idea?  If so, where would
be a good place to put the version information -- a
new "version=2013e" line after the POSIX TZ string?
If we are bumping from version '2' to 'version '3'
anyway, now may be a good time to add this, if it's
a good idea to add it that is.