[Development] QTimeZone fixes pushed to Release branch

[John Layt]

Hi,

I've pushed 4 fixes for QTimeZone to the release branch for review for 
inclusion in 5.0:

1) https://codereview.qt-project.org/#change,70984

Rather embarrassingly I misspelt the name Olson as Olsen, including in new 
public api for 5.2.  This patch fixes the public api and docs, but doesn't fix 
the private code to keep the patch against release as small as possible.

2) https://codereview.qt-project.org/#change,70985

This fixes a very inefficient loop under Windows that is needed for 3) and 4) 
below to pass CI tests without timing out.

3) https://codereview.qt-project.org/#change,70986

This fixes a crash on Linux for abbreviations in some time zones, and thus in 
QDateTime::toString().  It also adds a stress test that validates all 
available time zones.  This was previously approved against stable but not 
merged due to 2) causing CI failure.

4) https://codereview.qt-project.org/#change,70987

This fixes an infinite loop in converting to/from UTC for some time zones when 
used in QDateTime.  This was previously reviewed for stable but not merged due 
to 2).

Cheers!

John.