RFR(S): 8240734: ModuleHashes attribute not reproducible between builds

[Yangfei (Felix)]

Hi,

  We found module-info.class in java.base.jmod is not always consistent across different builds.  
  The ModuleHashes attribute in this module-info.class is not reproducible between builds.  
  Patch fixes the issue by using TreeMap instead of HashMap when computing ModuleHashes.  

  Bug: https://bugs.openjdk.java.net/browse/JDK-8240734 
  Webrev: http://cr.openjdk.java.net/~fyang/8240734/webrev.00/ 

  Passed tier1 test.  Please review.  

Thanks,
Felix