[tz] Update for tz-how-to.html?

Could we get an update to the tz-how-to.html document which: 1) Explains how to parse tzdata files for vanguard, rearguard, and standard versions? It looks like the way vanguard sections are not commented out, and rearguard sections are, that any third-party parser for tzdata is going to pick up vanguard zones and rules by default, rather than main. What I’d like to know how to parse the tzdata files, directly as they are found in a standard distribution, with rearguard, main, or vanguard results in mind, and without to run "make tarballs” to get a specific version. 2) Demonstrates the usage of the new ’s' and ‘d' suffixes in SAVE columns? Any help with these issues would be much appreciated. -Kerry