Fix SSE-detection for WinRT-64bit.

Change-Id: I97540ccb26d490be25904581f5f38bf4da2ceacc
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Add winrt-x64-msvc2012-mkspec.

Change-Id: I15443ecb7b3b6c74f07167758c32e4ee305848e2
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Fix qsystemdetection.h for WinRT-64bit apps.

Prevent them from being detected as Q_OS_WIN64.

Change-Id: Ie857bf1adb34e1510798bbaf9203e9a62578a499
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>