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.

include/flag.h

@@ -34,6 +34,7 @@ struct flag {
     boolean friday13;        /* it's Friday the 13th */
     boolean goldX;           /* for BUCX filtering, whether gold is X or U */
     boolean help;            /* look in data file for info about stuff */
+    boolean tips;            /* show helpful hints? */
     boolean ignintr;         /* ignore interrupts */
     boolean implicit_uncursed; /* maybe omit "uncursed" status in inventory */
     boolean ins_chkpt;       /* checkpoint as appropriate; INSURANCE */