Remove * in docstrings.
(prolog-program-name): Add SWI prolog.
(prolog-mode-menu): New menu.
(prolog-mode): Set comment-add.
(prolog-indent-line): Simplify. Use indent-line-to.
(inferior-prolog-buffer): New var.
(inferior-prolog-run, inferior-prolog-process): New funs.
(run-prolog, switch-to-prolog): Rewrite, using them.
(prolog-consult-region): Use inferior-prolog-buffer.
(inferior-prolog-load-file): New function.
(prolog-mode-map): Add bindings for load-file and switch-to-prolog.