RFR: 8245619: Remove unused methods in UnixNativeDispatcher

[Claes Redestad]

Hi,

this patch removes four orphaned methods from UnixNativeDispatcher that
are no longer used after the Solaris removal:

Webrev: http://cr.openjdk.java.net/~redestad/8245619/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8245619

Testing: tier1

Thanks!

/Claes