7041778: Move SCTP implementation out of sun.nio.ch and into its own package

[Chris Hegarty]

This CR will be used to move the SCTP Java implementation into its own 
package, from sun.nio.ch to sun.nio.ch.sctp. There is currently no 
restriction that libsctp cannot depend on libnet/nio, so the native 
implementation simply needs to reflect the new Java package structure.

As a consequence of moving the SCTP implementation into its own package 
some of the package private sun.nio.ch classes need to made public so 
the SCTP implementation can access them. Utility classes like IOStatus, 
IOUtil, Net, and Util. The SelChImpl interface that the SCTP channels 
implement, etc.

http://cr.openjdk.java.net/~chegar/7041778/webrev.00/webrev/

Thanks,
-Chris.