LP 1155611 - prevent unnecessary load of fm_IDL.xml

Ensure fm_IDL.xml is loaded only when IDL2js has not been loaded.

Modified for 2.3 and before to avoid using Object.keys(), which is not
supported in all browsers, but is needed by JSPAC.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>