Fix a bug where ::warning() was called with a va_list argument instead of an actual vararg list. Also cleaned up the format for warnings. (Previously some would start with "warning - warning - Warning:" which was a bit redundant)

module mini.norun_debug12;

interface I
{
    int foo();
}

class C : I
{
    int i = 24;
    int foo()
    {
        return i;
    }
}

void main()
{
    scope c = new C;
    I i = c;

    int* fail;
    *fail = 0;
}