pull request #798 - fix typo in disclosure \

of vanquired monsters.

Pull request from janne-hmp:  the test for how many spaces to insert
in front of "the <unique monster>" couldn't match prefix "the "
because it was specifying a length of 3 instead of the 4 required to
include the trailing space.

Despite that clear error, the code worked as intended because the
default value of 0 is the same as an explicit value of 0 it would
have gotten if it had matched "the ".  So there is no change in the
resulting vanquished monsters display.

Closes #798

src/insight.c

@@ -2744,7 +2744,7 @@ list_vanquished(char defquery, boolean ask)
                                 makeplural(mons[i].pmnames[NEUTRAL]));
                 }
                 /* number of leading spaces to match 3 digit prefix */
-                pfx = !strncmpi(buf, "the ", 3) ? 0
+                pfx = !strncmpi(buf, "the ", 4) ? 0
                       : !strncmpi(buf, "an ", 3) ? 1
                         : !strncmpi(buf, "a ", 2) ? 2
                           : !digit(buf[2]) ? 4 : 0;