RFR: 8000754: NPG: Implement a MemoryPool MXBean for Metaspace

[Erik Helin]

Hi,

this change implements a new MemoryManagerMXBean, MetaspaceManager, as
well as two new MemoryPoolMXBeans: Metaspace and Class Metaspace. I have
also written a tests that tests the new beans.

Webrev:
http://cr.openjdk.java.net/~ehelin/8000754/webrev.01/

Bug:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8000754

Testing:
JPRT
New jtreg test

Thanks,
Erik