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.

include/decl.h

@@ -561,14 +561,14 @@ struct trapinfo {
 };
 
 enum vanq_order_modes {
-    VANQ_MLVL_MNDX = 0,
-    VANQ_MSTR_MNDX,
-    VANQ_ALPHA_SEP,
-    VANQ_ALPHA_MIX,
-    VANQ_MCLS_HTOL,
-    VANQ_MCLS_LTOH,
-    VANQ_COUNT_H_L,
-    VANQ_COUNT_L_H,
+    VANQ_MLVL_MNDX = 0, /* t - traditional: by monster level */
+    VANQ_MSTR_MNDX,     /* d - by difficulty rating */
+    VANQ_ALPHA_SEP,     /* a - alphabetical, first uniques, then ordinary */
+    VANQ_ALPHA_MIX,     /* A - alpha with uniques and ordinary intermixed */
+    VANQ_MCLS_HTOL,     /* C - by class, high to low within class */
+    VANQ_MCLS_LTOH,     /* c - by class, low to high within class */
+    VANQ_COUNT_H_L,     /* n - by count, high to low */
+    VANQ_COUNT_L_H,     /* z - by count, low to high */
 
     NUM_VANQ_ORDER_MODES
 };
@@ -1562,7 +1562,6 @@ struct instance_globals_v {
 
     /* end.c */
     struct val_list valuables[3];
-    int vanq_sortmode;
 
     /* mhitm.c */
     boolean vis;