API: support options.match for delete action

Using 'options.match', you can update an existing contact based on its id, as described on: http://wiki.civicrm.org/confluence/display/CRMDOC/API+changes#APIchanges-4.4.0:%27create%27and%27replace%27actionsaccept%27options.match%27or%27options.match-mandatory%27

For example:
$result = civicrm_api('contact', 'create', array(
'version' => 3,
'contact_type' => 'Individual',
'first_name' => 'Newfirstname',
'external_identifier' => '1234',
'options' => array(
'match' => 'external_identifier',
),
));

It would be nice if the same could be done for entity deletions, e.g.:
$result = civicrm_api('contact', 'delete', array(
'version' => 3,
'external_identifier' => '1234',
'options' => array(
'match' => 'external_identifier',
),
));