build system support for WinRT

Done-With: Andrew Knight
Done-With: Oswald Buddenhagen

Change-Id: Ief4e921072a03229bb342480a85024a1fc09fa56
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>