RFR(M): 8059592: Recent bugfixes in ppc64 port.

[Lindenmaier, Goetz]

Hi,

This change contains some bugfixes in the ppc64 coding, and some minor
improvements.  It only touches code used in the port.
http://cr.openjdk.java.net/~goetz/webrevs/8059592-ppc_bugs/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8059592

Please review and test this change.  I please need a sponsor.
This change also should go to 8u40, please.

Best regards,
  Goetz.