Request for review (s) - 8003554

[Jon Masamitsu]

8003554: NPG: move Metablock and Metachunk code out of metaspace.cpp

http://cr.openjdk.java.net/~jmasa/8003554/webrev.00/

This moves code for Metablock and Metachunk out of metaspace.cpp and
into metablock.cpp and metachunk.cpp, respectively.

The only semantic change is the creation and use of
verify_chunk_size() which moves an assertion check
on the size of the Metachunk out of Metachunk::verify()
and into SpaceManager (for access to MediumChunk
and SmallChunk which belong to SpaceManager).