API dies with "Fatal error" since revision 5734

Since (atleast) revision 5734 the API returns a fatal error.

Fatal error: Call to undefined function authenticate() in /opt/observium/html/includes/api/functions.inc.php on line 169

Looks like the file authenticate.inc.php isn't included correctly anymore, or that the function moved.

Upgrade path incase that gives you more details:
– Updating database/file schema
150 -> 151 ... (db) done.
151 -> 152 ... (db) done.
152 > 153 ... (file) Converting RRD ds type for tcpCurrEstab COUNTER>GAUGE: ........
153 -> 154 ... (db) done.
154 -> 155 ... (db) done.
155 -> 156 ... (db) done.
– Done