Make extended commands return defined flags

Instead of returning 0 or 1, we'll now use ECMD_OK or ECMD_TURN.
These have the same meaning as the hardcoded numbers; ECMD_TURN
means the command uses a turn.

In future, could add eg. a flag denoting "user cancelled command"
or "command failed", and should clear eg. the cmdq.

Mostly this was simply replacing return values with the defines
in the extended commands, so hopefully I didn't break anything.

src/detect.c

@@ -1813,15 +1813,15 @@ dosearch0(int aflag) /* intrinsic autosearch vs explicit searching */
     return 1;
 }
 
-/* the 's' command -- explicit searching */
+/* the #search command -- explicit searching */
 int
 dosearch(void)
 {
     if (cmd_safety_prevention("another search",
                           "You already found a monster.",
                           &g.already_found_flag))
-        return 0;
-    return dosearch0(0);
+        return ECMD_OK;
+    return dosearch0(0) ? ECMD_TIME : ECMD_OK;
 }
 
 void