* lisp/progmodes/antlr-mode.el: Remove XEmacs compatibility

* lisp/progmodes/antlr-mode.el: Remove XEmacs compatibility

(cond-emacs-xemacs, cond-emacs-xemacs-macfn, defunx, ignore-errors-x):
Remove those functions and macros.  Replace every use with the result
of their use.
(antlr-default-directory): Remove function, use the `default-directory`
variable instead.
(antlr-read-shell-command): Remove function, use
`read-shell-command` instead.
(antlr-with-displaying-help-buffer): Remove function, by inlining it at
its only call site.
(antlr-end-of-rule, antlr-beginning-of-rule, antlr-end-of-body)
(antlr-beginning-of-body): Mark them as movement commands.