tests/4 qt: Force the use of -std=c++11
Qt5 now requires this, and if no -std option is passed to clang, it does
not enable C++ 11 features and we get a build failures.
-project('qt4 and 5 build test', 'cpp')
+project('qt4 and 5 build test', 'cpp',
+ # Qt5 now requires C++ 11 support
+ default_options : ['cpp_std=c++11'])
qt5_modules = ['Widgets']
foreach qt : ['qt4', 'qt5']
