Constify QDirSortItemComparator::operator() (used for sorting)

Change-Id: I7149ec2fdabdfcfa7d6f28b1105da154a333096f
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Windows: Use QSharedPointer for the dialog helpers.

The dialog thread can outlive the platform dialog helper if
the helper is destroyed. In that case, IFileDialog::Show()
returns since the parent window is destroyed and then tried
to emit signals on the destroyed helper class instance.
Pass a shared pointer to the native dialog instead of a pointer
to the helper class to the dialog.

Task-number: QTBUG-32494
Task-number: QTBUG-30513

Change-Id: I7c2e769460270a26d886fdefee93ea59c2a17196
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Windows: Add command line parameter enabling OS-synthesized mouse events from touch.

Applications launched with -platform windows:mousefromtouch will
receive OS-synthesized mouse events.

Task-number: QTBUG-31386
Change-Id: I1c49486589c4a7fa4fb5525f7a5adca09b1cfb89
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>