Qt sets -D_HAS_EXCEPTIONS=0 on MSVC 2013

Defining _HAS_EXCEPTIONS=0 is unsupported and causes a build error in MSVC 2013 headers, see for instance the build logs of https://codereview.qt-project.org/#/c/205744/

C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\INCLUDE\concrt.h(4774) : error C3861: '__uncaught_exception': identifier not found

See also https://connect.microsoft.com/VisualStudio/feedback/details/811347/compiling-vc-12-0-with-has-exceptions-0-and-including-concrt-h-causes-a-compiler-error

Macro _HAS_EXCEPTIONS=0 is undocumented and unsupported by Microsoft.

And also https://stackoverflow.com/questions/34273095/c-visual-studio-2012-issues