GUACAMOLE-422: Add errno header.
GUACAMOLE-422: Add errno header.

apache/guacamole-server,glyptodon/guacamole-server,mike-jumper/incubator-guacamole-server,glyptodon/guacamole-server,mike-jumper/incubator-guacamole-server,glyptodon/guacamole-server,mike-jumper/incubator-guacamole-server,apache/guacamole-server,apache/guacamole-server,mike-jumper/incubator-guacamole-server