new 'sortvanquished' option

Allow the preferred sort order for the vanquished monsters list to
be specified in the run-time config file
|OPTIONS=sortvanquished:X
where X is t, d, a, c, n, or z.  It can also be set to 'A' or 'C'
but those aren't documented and aren't offered as choices when
setting the value interactively, which can be done via 'm O' or by
using 'm #vanquished'.

Guidebook.mn has been updated but Guidebook.tex is lagging again.

dat/opthelp

@@ -251,6 +251,13 @@ sortloot      preferred order when examining a set of objects           [n]
               none -- no sorting
               loot -- sort piles of objects on floor and in containers
               full -- 'loot' plus objects in inventory
+sortvanquished preferred order when viewing vanquished monsters list    [t]
+              t -- traditional, order by monster level
+              d -- order by monster difficulty rating
+              a -- alphabetical, first any unique monsters then others
+              c -- order by class, low to high level within each class
+              n -- order by count, high to low
+              z -- order by count, low to high
 statushilites whether to display status highlights (when non-zero) and  [0]
               also how many turns to display temporary highlights (for
               'up', 'down', and 'changed' hilite_status rules)