Change-Id: I9a8d3113f0428294db847638365fb0233c93d9ac
&$legend: the legend text. Defaults to wfMessage( "prefs-$key" )->text() but may
be overridden
-'PrefixSearchBackend': Override the title prefix search used for OpenSearch and
+'PrefixSearchBackend': DEPRECATED! Override SearchEngine::completionSearchBackend instead.
+Override the title prefix search used for OpenSearch and
AJAX search suggestions. Put results into &$results outparam and return false.
$ns: array of int namespace keys to search in
$search: search term (not guaranteed to be conveniently normalized)