Added 'HH' and 'HZ' to the amino acid atom names in __det_pdb_element().
This is in response to Tiago Pais's <tpais att itqb dot unl dot pt> post at
https://mail.gna.org/public/relax-users/2009-11/msg00002.html (Message-id:
<AF0E494FAE984C0BB8D4C8CE521D621D@...>).
