GUACAMOLE-325: Check whether poll() is defined.
GUACAMOLE-325: Check whether poll() is defined.

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