Display names miss data in database on imports and API updates

Contact imports, and also the civicrm_contact_update API function, only use data passed in the import or API call when updating display names.

So, for example, if you have a contact "Prof. Juan Gomez QC", and you use the API or import to update the last name to "Gómez", his display name becomes simply "Gómez" - the prefix, suffix and first name in the database are ignored.

See http://forum.civicrm.org/index.php/topic,16545.0.html