Functions that modify the d-pointer must detach or otherwise take
measures to not modify the const, read-only shared_null.
The setSharable(bool) function takes care to detach when setting
sharable to false, but should avoid setting the sharable data member
unless d is not the shared null.
Similarly, QMap<Key, T>::setInsertInOrder() needs to detach if it is
shared with the shared_null (the logic has been updated to be the same
as setSharable()).
Change-Id: Ida5cb9818b86695f1b9f0264418b955c56424898
Reviewed-on: http://codereview.qt-project.org/5929
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>
