Apply sysconf EXPLORERS restriction on startup

The sysconf EXPLORERS list restricting access to explore mode was being
evaluated and used when a player used the #exploremode command in-game,
or when specifying -X or OPTIONS=playmode:explore on the command line
when resuming a normal game, but not when starting an entirely new game.
When SYSCF is avilable, check for authorization early, similar to debug
mode authorization, to restrict access to explore mode to EXPLORERS
under (hopefully) all circumstances.

src/cmd.c

@@ -965,10 +965,7 @@ enter_explore_mode(void)
     } else {
         const char *oldmode = !wizard ? "normal game" : "debug mode";
 
-#ifdef SYSCF
-#if defined(UNIX)
-        if (!sysopt.explorers || !sysopt.explorers[0]
-            || !check_user_string(sysopt.explorers)) {
+        if (!authorize_explore_mode()) {
             if (!wizard) {
                 You("cannot access explore mode.");
                 return ECMD_OK;
@@ -978,8 +975,6 @@ enter_explore_mode(void)
                 /* keep going */
             }
         }
-#endif
-#endif
         pline("Beware!  From explore mode there will be no return to %s,",
               oldmode);
         if (paranoid_query(ParanoidQuit,

src/options.c

@@ -10257,11 +10257,14 @@ set_playmode(void)
             gp.plnamelen = (int) strlen(strcpy(gp.plname, "wizard"));
         else
             wizard = FALSE; /* not allowed or not available */
-        /* force explore mode if we didn't make it into wizard mode */
+        /* try explore mode if we didn't make it into wizard mode */
         discover = !wizard;
         iflags.deferred_X = FALSE;
     }
-    /* don't need to do anything special for explore mode or normal play */
+    if (discover && !authorize_explore_mode()) {
+        discover = iflags.deferred_X = FALSE;
+    }
+    /* don't need to do anything special for normal play */
 }
 
 static void

src/restore.c

@@ -560,8 +560,8 @@ restgamestate(NHFILE *nhfp)
     if (newgameflags.debug) {
         /* authorized by startup code; wizard mode exists and is allowed */
         wizard = TRUE, discover = iflags.deferred_X = FALSE;
-    } else if (wizard) {
-        /* specified by save file; check authorization now */
+    } else if (wizard || discover) {
+        /* specified by save file; check authorization now. */
         set_playmode();
     }
     role_init(); /* Reset the initial role, race, gender, and alignment */