add this back

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2456 a5045d30-4826-4484-9c7f-6e55a06ddc77
update MolOps.cpp for older boost version

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2457 a5045d30-4826-4484-9c7f-6e55a06ddc77