[8u40] Request approval: 8044473: Allow for extended set of platform MXBeans

[Brent Christian]

Please approve this fix for 8u-dev.

Bug: https://bugs.openjdk.java.net/browse/JDK-8044473

Review: 
http://mail.openjdk.java.net/pipermail/serviceability-dev/2014-June/014984.html

Note this is new work for 8u40 - it is expected that the changes needed 
for JDK 9 will be different.  There are no new public APIs or MXBeans.

Thanks,
-Brent