RFR: Backport of JDK-6311046 & JDK-8046662

[David Simms]

The backport of the fix for 6311046 did not apply cleanly to 
"jdk8u/hs-dev", so I'm requesting a review of the changes.

Patch conflict occurred in os.cpp:526, but was just code to be removed 
by the fix, so no big deal.

8046662 must follow 6311046.

Bug: https://bugs.openjdk.java.net/browse/JDK-6311046
Bug: https://bugs.openjdk.java.net/browse/JDK-8046662

Web review (combined): 
http://cr.openjdk.java.net/~dsimms/8u_6311046_8046662/

Original 6311046: http://cr.openjdk.java.net/~dsimms/6311046/rev5/

Thanks
/David Simms