Use define-minor-mode where applicable.

Use define-minor-mode where applicable.
* mh-show.el (mh-showing-mode): Move function to mh-e.el.
* mh-e.el (mh-showing-mode):
* url-dired.el (url-dired-minor-mode):
* org-table.el (orgtbl-mode):
* view.el (view-mode):
* type-break.el (type-break-query-mode)
(type-break-mode-line-message-mode):
* textmodes/reftex.el (reftex-mode):
* term/vt100.el (vt100-wide-mode):
* tar-mode.el (tar-subfile-mode):
* savehist.el (savehist-mode):
* ibuf-ext.el (ibuffer-auto-mode):
* composite.el (auto-composition-mode):
* progmodes/vhdl-mode.el (vhdl-electric-mode, vhdl-stutter-mode):
Use define-minor-mode.
(vhdl-mode): Use static mode-line format.
(vhdl-mode-line-update): Delete.
(vhdl-create-mode-menu, vhdl-activate-customizations)
(vhdl-hs-minor-mode): Don't bother calling it.