redundant "guard appears" messages

When a vault guard was created it was producing a "guard appears"
message, then the vault code immediately produced a "vault's guard
enters" message.  Suppress the creation message.

While testing that, I noticed that if the hero was blind and lacked
telepathy, "someone enters" started the guard interrogation sequence
but if hero answered and dropped gold, the way out wasn't discernable.
Put a "remembered, unseen monster" glyph at the guard's spot in the
breeched vault wall.  The player will need to do <search><move> over
and over to actually follow the guard but at least will know where to
start doing that.

doc/fixes3-7-0.txt

@@ -1,4 +1,4 @@
-HDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.952 $ $NHDT-Date: 1655503067 2022/06/17 21:57:47 $
+HDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.975 $ $NHDT-Date: 1657868310 2022/07/15 06:58:30 $
 
 General Fixes and Modified Features
 -----------------------------------
@@ -963,6 +963,8 @@ similarly, if #wizfliplevel was used to transpose an active level while a
 blessed potion of polymorph will prompt user for monster to poly into
 out of array bounds access attempt occurred when deciding whether to bounce
 	if wand or spell zap reached edge of map
+if blind hero was challanged by a vault guard, it wasn't possible to see how
+	to start following that guard out of the vault
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/vault.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	vault.c	$NHDT-Date: 1606009006 2020/11/22 01:36:46 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.77 $ */
+/* NetHack 3.7	vault.c	$NHDT-Date: 1657868307 2022/07/15 06:58:27 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.91 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2011. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -295,7 +295,7 @@ invault(void)
 {
     struct monst *guard;
     struct obj *otmp;
-    boolean gsensed;
+    boolean spotted;
     int trycount, vaultroom = (int) vault_occupied(u.urooms);
 
     if (!vaultroom) {
@@ -370,7 +370,7 @@ invault(void)
         }
 
         /* make something interesting happen */
-        if (!(guard = makemon(&mons[PM_GUARD], x, y, MM_EGD)))
+        if (!(guard = makemon(&mons[PM_GUARD], x, y, MM_EGD | MM_NOMSG)))
             return;
         guard->isgd = 1;
         guard->mpeaceful = 1;
@@ -402,19 +402,24 @@ invault(void)
             (*func)("%s shatter.",
                     (bcnt == 1) ? an(bname) : makeplural(bname));
         }
-        gsensed = !canspotmon(guard);
+        spotted = canspotmon(guard);
-        if (!gsensed)
+        if (spotted) {
             pline("Suddenly one of the Vault's %s enters!",
                   makeplural(pmname(guard->data, Mgender(guard))));
-        else
+            newsym(guard->mx, guard->my);
+        } else {
             pline("Someone else has entered the Vault.");
-        newsym(guard->mx, guard->my);
+            /* make sure that hero who can't see the guard knows where the
+               wall is breeched, otherwise we couldn't follow the guard out;
+               the breech isn't necessarily adjacent to the hero */
+            map_invisible(guard->mx, guard->my);
+        }
 
         if (u.uswallow) {
             /* can't interrogate hero, don't interrogate engulfer */
             if (!Deaf)
                 verbalize("What's going on here?");
-            if (gsensed)
+            if (!spotted)
                 pline_The("other presence vanishes.");
             mongone(guard);
             return;
@@ -671,11 +676,13 @@ wallify_vault(struct monst *grd)
 static void
 gd_mv_monaway(struct monst *grd, int nx, int ny)
 {
-    if (MON_AT(nx, ny) && !(nx == grd->mx && ny == grd->my)) {
+    struct monst *mtmp = m_at(nx, ny);
+
+    if (mtmp && mtmp != grd) {
         if (!Deaf)
             verbalize("Out of my way, scum!");
-        if (!rloc(m_at(nx, ny), RLOC_ERR|RLOC_MSG) || MON_AT(nx, ny))
+        if (!rloc(mtmp, RLOC_ERR | RLOC_MSG) || MON_AT(nx, ny))
-            m_into_limbo(m_at(nx, ny));
+            m_into_limbo(mtmp);
     }
 }
 
@@ -774,15 +781,14 @@ gd_move_cleanup(
     int x, y;
     boolean see_guard;
 
-    /* The following is a kludge.  We need to keep    */
+    /*
-    /* the guard around in order to be able to make   */
+     * The following is a kludge.  We need to keep the guard around in
-    /* the fake corridor disappear as the player      */
+     * order to be able to make the fake corridor disappear as the
-    /* moves out of it, but we also need the guard    */
+     * player moves out of it, but we also need the guard out of the
-    /* out of the way.  We send the guard to never-   */
+     * way.  We send the guard to never-never land.  We set ogx ogy to
-    /* never land.  We set ogx ogy to mx my in order  */
+     * mx my in order to avoid a check at the top of this function.
-    /* to avoid a check at the top of this function.  */
+     * At the end of the process, the guard is killed in restfakecorr().
-    /* At the end of the process, the guard is killed */
+     */
-    /* in restfakecorr().                             */
     x = grd->mx, y = grd->my;
     see_guard = canspotmon(grd);
     parkguard(grd); /* move to <0,0> */