rpl-mode: local mode map

To make inserting slashes and stars less painful, override their keys.

Add C-c prefix commands for making delimited thing pairs.
rpl-mode: remove &->"AND" shortcut
rpl-mode: `rpl-insert-balanced-program-delimiters' adds a newline

Program delimiters are added and the cursor is positioned the same way
the calculator does.
rpl-mode: shortcut to add balanced parentheses
(incomplete) rpl-mode: pretty print trigraphs

When the symbol `rpl-pretty-trigraphs' is non-NIL trigraphs are
displayed using UTF-8 counterparts.

Not all of the trigraphs have been added to this (mostly the huge number
of Greek characters).