7187429: NMT ON: Merge failure should cause NMT to shutdown
Summary: Fixed NMT assertion failures
Reviewed-by: acorn, kvn

Summary: Changed _query_lock to heap object from static object. Also fixed _query_lock and snapshot lock ranks, so they can participate deadlock detection.
Reviewed-by: coleenp, dholmes, kvn

7151532: DCmd for hotspot native memory tracking
Summary: Implementation of native memory tracking phase 1, which tracks VM native memory usage, and related DCmd
Reviewed-by: acorn, coleenp, fparain