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 bug4;

int func(int i)
{
    i += 2;
    i -= 3;
    return i;
}

void main()
{
    assert(func(4) == 3);
}