Tips and option to disable them

Adds a more general way to handle gameplay tips, and adds
a boolean option "tips", which can be used to disable all
tips.  Adds a helpful longer message when the game goes
into the "farlook" mode.

Also adds a lua binding to easily show multi-line text
in a menu window.

Breaks save compat.

doc/Guidebook.tex

@@ -4957,6 +4957,9 @@ screen.  (Applies to ``tty'' and ``curses'' interfaces only; ``X11'' interface a
 uses a timer-based delay.  The default is on if configured into the
 program.)  Persistent.
 %.lp
+\item[\ib{tips}]
+Show some helpful tips during gameplay (default on).  Persistent.
+%.lp
 \item[\ib{tombstone}]
 Draw a tombstone graphic upon your death (default on).  Persistent.
 %.lp