8199791: (se) More Selector cleanup

[Alan Bateman]

This is another batch of cleanup to the Selector implementations.

A significant part of the cleanup is changing the epoll and kqueue based 
Selector implementations to use the EPoll and KQueue support classes. 
This eliminate their wrapper classes and several native methods. The 
result is much smaller implementations. The queuing of changes to the 
interest set has also been re-worked to avoid needing cancellation 
needing to kill all pending updates. A few of the Selector 
implementations had a native method to write a byte to one end of the 
pipe used for the wakeup mechanism. This has been changed to use 
IOUtil.write1 instead. Interrupting timed polls (as in EINTR, not Thread 
interrupt) wasn't handled correctly in some of the implementations so 
that has been re-worked.

The webrev with the changes is here:
     http://cr.openjdk.java.net/~alanb/8199791/webrev/index.html

I have several other changes for this area but I'd prefer to do the 
changes in small batches to avoid changing too much in one go. Small 
patches are easier to review too of course (and in this case, there is 
more deletion than new code).

I have run all tests on all platforms several times.

-Alan