GUACAMOLE-518: Remove unused GUAC_KEYSYMS_* constants.
GUACAMOLE-518: Remove unused GUAC_KEYSYMS_* constants.

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