Remove XEmacs compat code from idlwave.el

Remove XEmacs compat code from idlwave.el

idlwave.el: (idlwave-comment-line-start-skip, idlwave-mode-map)
(idlwave-mode, idlwave-get-buffer-visiting)
(idlwave-find-file-noselect, idlwave-complete-in-buffer)
(idlwave-attach-classes, idlwave-popup-select)
(idlwave-split-menu-emacs, idlwave-display-completion-list)
(idlwave-default-choose-completion)
(idlwave-display-completion-list-emacs)
(idlwave-display-completion-list-1)
(idlwave-make-modified-completion-map-emacs)
(idlwave-class-file-or-buffer, idlwave-rinfo-mouse-map)
(idlwave-display-calling-sequence)
(idlwave-insert-source-location)
(idlwave-list-load-path-shadows, idlwave-edit-in-idlde): Remove
XEmacs compat code.