Add IoBuffer.putUnsigned* methods to balance the getUnsigned* methods for completeness

While unsigned integers types are quite meaningful in networking protocols, Java does not provide unsigned integer primitive types. The IoBuffer.getUnsigned* methods are filling the gap between the need of unsigned integers and the real Java programs.

But IoBuffer does not provide the correlative IoBuffer.putUnsigned* methods. Thus for completeness, this issue proposes to add those IoBuffer.putUnsigned* methods.

Rgds