relax SVN archive

Added the missing return_name and return_warnings args to the structural API bond_vectors() method.

Modified the print out during the extraction of bond vectors.

Fix for the bond_vectors() method - the spin.attached_atom variable is correctly set.

Modified vectors() to use the new data returned by cdp.structure.bond_vectors().

Modified the __find_bonded_atom() and bond_vectors() methods to return more data.

This additional data is the name of the attached atom and any warnings when trying to find the
attached atom.

Added 2 new methods to the internal relax structural object.

These are __find_bonded_atom() and bond_vectors().

Changed calls to write_pdb_file() to its actual name: write_pdb().

Corrections for the atom_connect() function calls to match the needed variables.

Correction for the structure.atom_add() function calls to match the variables needed.

Switched from os.devnull to devnull within relax_io.open_write_file().

This is as proposed by Edward d'Auvergne in a post at:
https://mail.gna.org/public/relax-devel/2008-07/msg00021.html (Message ID:
7f080ed10807061152i2a101224p5c5d710d6a92ee@...)