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.

doc/fixes3-7-0.txt

@@ -1912,6 +1912,8 @@ very large humanoids can wear mummy wrappings
 for ranger characters, shooting any type of arrow while wielding the Longbow
 	of Diana gets an extra +1 to multi-shot
 change the #vanquished command from debug-only to general user command
+add 'sortvanquished' option to be able to set the preferred sort order without
+	using 'm #vanquished' and to have it persist across save/restore
 have 'I u' mention whether there are any unpaid items on the floor (unusual
 	but not impossible); it doesn't itemize them or show shop price