GH 9016: Bitwise operation weirdness
Series now supports bitwise op for integral types. 

I have made the changes in wrapper() itself instead of na_op() because it looked to me like wrapper is controlling the input and output fill and dtype. Once that is taken care of, na_op() seems to be doing the right thing by itself and so I did not have to change anything to get back the expected behavior. Happy to change if things need to be altered toward better design etc.
