Allow to use PollSelector on BSD as well

[normanmaurer]

PollSelector should work on linux and bsd. Could you allow to use PollSelector on BSD as well ? Maybe by adding another SelectoProvider which always return the PollSelector ?

[headius]

Indeed. Let's do this for 0.14. Help?

[Low-power]

I think this should be made user-configurable by reading a system property, so the user may switch to a non-default Selector implementation by adding a -Djnr.enxio.... option to JVM.

[headius]

@Low-power Yes that seems reasonable. I think the only tricky bit is making sure the mappings also work on BSD.