[svn r183] Fixed broken identity expressions with two pointers of different types. Fixed broken pointer arithmetic for subtraction (tango.text.Util unittest now passes)

module with1;
struct S
{
    int i;
    float f;
}
void main()
{
    S s;
    with(s)
    {
        i = 0;
        f = 3.4;
    }
}