back to the original fp hashing scheme + atom degrees

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2453 a5045d30-4826-4484-9c7f-6e55a06ddc77
further optimization; switch back to the original hashing scheme

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2454 a5045d30-4826-4484-9c7f-6e55a06ddc77