Merged in changes from development repository:

Finished implementing the `delete handle_value' and `undelete handle_value' commands.

In |purge_server_database|:

   Added code for deleting individual handle values that have been marked for deletion and expired.
   These are handle values that have been marked for deletion using the \.{delete handle\_value} command,
   which I have now added.

   Previously, this function only accounted for the case that handle values had been marked for deletion
   by means of the \.{delete handle} command, in which case all of the handle values belonging to the
   handle in question are marked.  This was the only possibility until now.