RFR - 8142872: Remove support for sun.nio.ch.PollSelectorProvider from 9

[Rob McKenna]

Hi folks,

 From time to time we get bugs on PollSelectorProvider despite 
recommending people use alternative implementations. The only way it can 
be used is setting the following system property:

-Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.PollSelectorProvider

Superior SelectorProvider implementations exist for all Oracle JDK 
platforms and PollSelectorProvider should not be used on those platforms 
if at all possible. That being the case we'd like to pull it from the 
default build:

http://cr.openjdk.java.net/~robm/8076282/

	-Rob