[9] Review request for 8164937: Remove code from SortingFocusTraversalPolicy that hacks into non-public Arrays.legacyMergeSort

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:
bug: https://bugs.openjdk.java.net/browse/JDK-8164937

webrev: http://cr.openjdk.java.net/~ssadetsky/8164937/webrev.00/

The "hack" is removed and replaced with a copy of the merge sort 
implementation from the java.util.Arrays.

--Semyon