rpl-mode: trigraph handling and ports

These are all the trigraphs (and the humorously named '\\') that the
ASCII reader knows about.  If something that should have been a trigraph
is given without it, fontify it as a warning.

Variables with port number are fontified as variables.  Illegal uses of
':' are warnings.

Stack manipulation is no longer fontified as a keyword.  Too much
coloring of text to make it stand out in heavy stack manipulation
programs.
rpl-mode: magic-mode-alist

Since ASCII files will have "%%HP:" starting the first line, we can use
`magic-mode-alist' to enter the major mode regardless of the file
extension.
rpl-mode: allow trigraphs in port'd names
rpl-mode: add header and footer

The standard Emacs Lisp library header and footer.  Commentary on known
shortcomings and how to use the library is included.