QDateTimeParser fails to set correct zone when parsing with a zone specified

When a date-time format string includes a t specifier for the time-zone, and the string being parsed contains a time-zone specifier, the returned time-zone object should have its timeSpec() and related properties set to match;

• if the zone specifier is 'Z' (for "Zulu time", an alias for UTC), UTC or ±0:0, timeSpec() should be Qt::UTC;
• if the zone specifier is any other UTC-offset zone identifier, or a ±hh:mm offset, timeSpec() should be Qt::OffsetFromUTC
• if the zone specifier is a zone-name, timeSpec() should be Qt::TimeZone and timeZone() should report the correct zone.

Experiment reveals that, at least in the 'Z' case, this is not what happens.

Also, the t format-specifier for zone is documented in the wrong place - it is documented in the QTime::fromString() with string format (not enum); it should actually be documented in the matching QDateTime::fromString(), since that's the only case where it's meaningful. The parser should also only support it for the date-time case.