Replaced FIRST_PHANTOM_PROPERTY_TYPE by a predicate. Removed the (hopefully)
last default cases for switches on PropertyType. Benchmarks show that both
changes are performace-neutral.

Now every value of PropertyType should either be handled by an explicit case in
a switch or by an equality operator. Therefore, the C++ compiler should finally
be able to tell us which places to touch when changing PropertyType.

Review URL: http://codereview.chromium.org/8506004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9930 ce2b1a6d-e550-0410-aec6-3dcde31c8c00