RFR: 8013120 NMT: Kitchensink crashes with assert(next_region == NULL || !next_region->is_committed_region()) failed: Sanity check

[Zhengyu Gu]

NMT expects all committed regions are uncommitted before the whole 
reserved region can be released. It was the case until 8011268.

This change allows NMT to handle the scenario that virtual memory is 
being released while there are committed segments within the reserved 
region.

It also fixed a missing virtual memory tag when ArrayAllocator allocates 
from virtual memory.

Bug: http://bugs.sun.com/view_bug.do?bug_id=8013120
Webrev: http://cr.openjdk.java.net/~zgu/8013120/webrev.00/ 
<http://cr.openjdk.java.net/%7Ezgu/8013120/webrev.00/>

Thanks,

-Zhengyu