[tz] Future tzfile format

[Alan Barrett]

On Thu, 12 Sep 2013, Clive D.W. Feather wrote:
> What's wrong with XML. Parsers are easy to obtain.

Please not XML.  The tzfile parser needs to be lightweight, 
whereas XML parsers tend to be large, or limited to a subset of 
the format.

> The code that interprets the structure can ignore any entity 
> they don't understand, giving complete extensibility.

You can do the same with simple binary formats, such as 
Type-Length-Value, and you can have a bit in the type field to 
say ...

> "if you don't know what an 'abc' is, raise an error now rather 
> than trying to understand the contents".

--apb (Alan Barrett)