Reorganize object type enum, such that proxies are no longer in the middle

Reorganize object type enum, such that proxies are no longer in the middle
of the range of proper JS objects.

Unfortunately, callable types no longer form a range now. However, there
are only two anyway. We put them at either end of the range of JS object
types so that certain compares can be combined.

R=erik.corry@gmail.com,kmillikin@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/7737036

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9370 ce2b1a6d-e550-0410-aec6-3dcde31c8c00