we know that both sides are Smi and those where we don't.  Fix inlined
symbol table probes to cope with strings, undefined and null (indicating
a deleted entry).  Some changes to other architectures that were found
with the new asserts.
Review URL: http://codereview.chromium.org/6682026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7172 ce2b1a6d-e550-0410-aec6-3dcde31c8c00