[tz] version information in tz binary file?

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.