Delete some XEmacs compat code from mh-e/*.el

Delete some XEmacs compat code from mh-e/*.el

* lisp/mh-e/mh-acros.el (mh-mark-active-p):
* lisp/mh-e/mh-comp.el (mh-insert-x-mailer):
* lisp/mh-e/mh-compat.el (mh-define-obsolete-variable-alias)
(mh-make-obsolete-variable):
* lisp/mh-e/mh-folder.el (mh-folder-mode-map)
(mh-remove-xemacs-horizontal-scrollbar, mh-folder-mode):
* lisp/mh-e/mh-gnus.el (mh-gnus-local-map-property):
* lisp/mh-e/mh-show.el (mh-show-mode):
* lisp/mh-e/mh-utils.el (mh-colors-available-p):
* lisp/mh-e/mh-xface.el (mh-show-xface-function): Delete some
XEmacs compat code.