Added new $GLOBALS['acf_save_lock'] to ensure the acf/save_post action is only run on the post you are saving, not an attachment you are inserting during the save process

Signed-off-by: Elliot Condon <e@elliotcondon.com>
Select field: Fixing choices ':' explode function

Signed-off-by: Elliot Condon <e@elliotcondon.com>