RFR(M): 8136725 Provide utility for creation a counted loop reserve copy (clone)

[Igor Veresov]

Provide utility for creation a counted loop reserve copy (clone).
May be used in any graph optimization for simple roll back to the original loop, in partially will be used in SuperWord, where the loop modification goes on-the-fly and potentially may not finish correctly (the patch for SuperWord is coming soon).

This is contributed by Jan Civlin <jan.civlin at intel.com>

Webrev: http://cr.openjdk.java.net/~iveresov/loop-reverse/webrev-091515/

igor