Detecting timezone based on VTIMEZONE values

[evert]

Since forever we've been mapping VTIMEZONE objects to PHP timezones based on the TZID, X-LIC-* properties and others.

This system works pretty well, but every now and then we run across a VTIMEZONE object that we don't support. For those we should really fall back on parsing VTIMEZONE objects and figuring which PHP timezone they map to based on their values.

See #247

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[gjn]

+1 from me

[DominikTo]

Related to #44.
Also some previous research here: https://gist.github.com/SimonSimCity/9950755

[j03k64]

👍