Add a `Windows_tz` module containing a CLDR-sourced mapping table from
Windows timezone names to canonical IANA names. Update
`timedesc_of_timestamp` to resolve Windows-style timezone identifiers
(e.g. `"W. Europe Standard Time"`) via this table before constructing a
`Timedesc.Time_zone.t`, falling back to the local timezone with a
warning if resolution fails entirely.
Paolo Donadeo
dc11e077bf