1) addresses various Mark's concern;
2) adds some missing instance types and rearranges existing ones to follow
  InstanceType order;
3) various minor cleanups.

Review URL: http://codereview.chromium.org/3119023

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5286 ce2b1a6d-e550-0410-aec6-3dcde31c8c00