qsimd: Fix compilation with MinGW 64.

Task-number: QTBUG-34856
Change-Id: Ie1dbeb5787e1a60aeaca585160319bbe0943e2cb
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Kernel: Fix gcc warning in qsharedmemory_win.cpp

Fix gcc 4.7 'arning: converting 'false' to pointer type 'HANDLE {aka void*}' [-Wconversion-null]'

Change-Id: I28d890d5fd4975517a9329d68c9ef73f6fadf36c
Reviewed-by: Qt Doc Bot <qt_docbot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
(cherry picked from qtbase/baf8a2fbf710314096832b0ee5735ffdc8b24210)