Removed the following defines from en.inc.php, as I do not believe
they are used elsewhere in the source code. Refs #519.
                               ANONYMOUS_USER                   0
                           BUTTON_NEW_COMMENT                   0
                         BUTTON_REPLY_COMMENT                   0
                        BUTTON_RETURN_TO_NODE                   0
                         BUTTON_SEND_PW_LABEL                   0
                      BUTTON_SHOW_DIFFERENCES                   0
                          CHANGE_BUTTON_LABEL                   0
                      CHANGE_PASSWORD_HEADING                   0
                            COMMENT_ACL_LABEL                   0
                       COMMENT_AUTHOR_DIVIDER                   0
                       CURRENT_PASSWORD_LABEL                   0
                               DIFF_ADDITIONS                   0
                               DIFF_DELETIONS                   0
                              DIFF_LINK_TITLE                   0
                    DISPLAY_COMMENTS_THREADED                   0
                                    EDITED_BY                   0
                          ERROR_ACL_READ_INFO                   0
                     ERROR_DURING_FILE_UPLOAD                   0
                             ERROR_EMPTY_USER                   0
                            ERROR_FILE_EXISTS                   0
                  ERROR_MAX_FILESIZE_EXCEEDED                   0
                  ERROR_NON_EXISTENT_USERNAME                   0
                      ERROR_NOT_EXISTING_PAGE                   0
                       ERROR_NO_FILE_UPLOADED                   0
                        ERROR_NO_FILE_UPLOADS                   0
                         ERROR_NO_READ_ACCESS                   0
                     ERROR_OLD_PASSWORD_WRONG                   0
                        ERROR_OVERWRITE_ALERT                   0
                        ERROR_USERNAME_EXISTS                   0
                             ERROR_WRONG_HASH                   0
                         FREEMIND_PROJECT_URL                   0
                          INPUT_BUTTON_CANCEL                   0
                         INPUT_SUBMIT_PREVIEW                   0
                          INPUT_SUBMIT_REEDIT                   0
                           INPUT_SUBMIT_STORE                   0
                              LABEL_EDIT_NOTE                   0
                                  LABEL_ERROR                   0
                             LASTEDIT_MESSAGE                   0
                           LOGIN_BUTTON_LABEL                   0
                                LOGIN_HEADING                   0
                       LOGIN_REGISTER_HEADING                   0
                          LOGOUT_BUTTON_LABEL                   0
                                 MAX_DATETIME                   0
                                 MIN_DATETIME                   0
                      NEW_USER_REGISTER_LABEL                   0
                                NOT_AVAILABLE                   0
                                NOT_INSTALLED                   0
                             PASSWORD_CHANGED                   0
                      PASSWORD_REMINDER_LABEL                   0
                               PREVIEW_HEADER                   0
                                  QUICK_LINKS                   0
                          QUICK_LINKS_HEADING                   0
                                RAW_LINK_DESC                   0
                  REGISTERED_USER_LOGIN_LABEL                   0
                        REGISTER_BUTTON_LABEL                   0
                       REGISTRATION_SUCCEEDED                   0
                    RETRIEVE_PASSWORD_HEADING                   0
                    RETRIEVE_PASSWORD_MESSAGE                   0
                             REVERTLINK_TITLE                   0
                              REVISION_NUMBER                   0
                    RSS_RECENTCHANGES_VERSION                   0
                            SEARCH_TIPS_TITLE                   0
                                  SIMPLE_DIFF                   0
                          TITLE_REVISION_LINK                   0
                                        TODAY                   0
                        UPDATE_SETTINGS_INPUT                   0
                              USER_LOGGED_OUT                   0
                        USER_SETTINGS_HEADING                   0
                         USER_SETTINGS_STORED                   0
                     WIKKA_NO_PAGES_FOUND_FOR                   0