[tz] Howard Hinnant's Time Zone Database Parser

[Paul Eggert]

On 12/3/19 3:12 PM, Arthur David Olson wrote:

>         If |AUTO_DOWNLOAD| is |1| then first access to the timezone
>         database will install it if it hasn't been installed, and if it
>         has, will use the remote API to install the latest version if
>         not already installed.

You're right, that's somewhat concerning, as iana.org is not set up to 
handle HTTPS requests from a lot of clients. Perhaps Howard can be 
talked into making his parser's default URL point somewhere else 
(GitHub?) instead of to iana.org. I'll CC: this message to him.

Also, although that parser scrapes the current version number from 
<https://www.iana.org/time-zones>, that web page's format is not 
standardized and might change. It would be more reliable to get the 
latest version number from 
<https://data.iana.org/time-zones/data/version>, or to get the latest 
version (including its version number) from 
<https://www.iana.org/time-zones/repository/tzdata-latest.tar.gz>.