Added a stripModifiers() function to remove shared|const|immutable storage classes in D2 (should eventually be moved to a dhelpers file rather than llvm helpers). Replaced a few occurances of STCinvariant with STCimmutable.

module nested1;

void func(int i)
{
    (){
        assert(i == 3);
    }();
}

void main()
{
    func(3);
}