Extend disabling of whole-program-optimizations to MSVC 2013

Building with whole-program-optimizations remains a problem with MSVC
2013, so we must continue to disable it.

Task-number: QTBUG-35835
Change-Id: Ic3131495ce0ce323ad041e51332969cc01b741c5
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>