[QBS] C++11 support

[Ruslan Nigmatullin]

Hi all!

QBS currently doesn't support C++11 for applications built by it, so every project must write such code:

Properties {
    condition: qbs.toolchain.contains('gcc') && qbs.hostOS.contains("osx")
    cpp.cxxFlags: [ "-std=c++11", "-stdlib=libc++" ]
}
Properties {
    condition: qbs.toolchain.contains('gcc') && !qbs.hostOS.contains("osx")
    cpp.cxxFlags: [ "-std=c++11" ]
}

May be it's a good idea to add boolean option "cpp.cxx11Support" to cpp module?

--
Ruslan Nigmatullin