Prevent monster generation in the sokoban trap hallway

Makes Sokoban far less tedious when you don't have to worry about
monsters randomly popping up in the trap hallway while you're pushing
the boulder.

Adds a new exclusion zone for monster generation, and the goodpos
routine avoids the zones when GP_AVOID_MONPOS is used.

src/makemon.c

@@ -129,7 +129,7 @@ m_initgrp(
          * are peaceful and some are not, the result will just be a
          * smaller group.
          */
-        if (enexto(&mm, mm.x, mm.y, mtmp->data)) {
+        if (enexto_gpflags(&mm, mm.x, mm.y, mtmp->data, mmflags)) {
             mon = makemon(mtmp->data, mm.x, mm.y, (mmflags | MM_NOGRP));
             if (mon) {
                 mon->mpeaceful = FALSE;

src/mkmaze.c

@@ -26,7 +26,6 @@ staticfn void stolen_booty(void);
 staticfn boolean maze_inbounds(coordxy, coordxy);
 staticfn void maze_remove_deadends(xint16);
 staticfn void populate_maze(void);
-staticfn boolean is_exclusion_zone(xint16, coordxy, coordxy);
 
 /* adjust a coordinate one step in the specified direction */
 #define mz_move(X, Y, dir) \
@@ -302,7 +301,7 @@ maze0xy(coord *cc)
     return;
 }
 
-staticfn boolean
+boolean
 is_exclusion_zone(xint16 type, coordxy x, coordxy y)
 {
     struct exclusion_zone *ez = sve.exclusion_zones;

src/sp_lev.c

@@ -5446,10 +5446,10 @@ int
 lspo_exclusion(lua_State *L)
 {
     static const char *const ez_types[] = {
-        "teleport", "teleport-up", "teleport-down", NULL
+        "teleport", "teleport-up", "teleport-down", "monster-generation", NULL
     };
     static const int ez_types2i[] = {
-        LR_TELE, LR_UPTELE, LR_DOWNTELE, 0
+        LR_TELE, LR_UPTELE, LR_DOWNTELE, LR_MONGEN, 0
     };
     struct exclusion_zone *ez = (struct exclusion_zone *) alloc(sizeof *ez);
     lua_Integer x1,y1,x2,y2;

src/teleport.c

@@ -172,6 +172,9 @@ goodpos(
     /* skip boulder locations for most creatures */
     if (sobj_at(BOULDER, x, y) && (!mdat || !throws_rocks(mdat)))
         return FALSE;
+    /* pretend GP_AVOID_MONPOS == monster creation */
+    if (avoid_monpos && is_exclusion_zone(LR_MONGEN, x, y))
+        return FALSE;
 
     return TRUE;
 }
@@ -194,6 +197,17 @@ enexto(
             || enexto_core(cc, xx, yy, mdat, NO_MM_FLAGS));
 }
 
+boolean
+enexto_gpflags(
+    coord *cc,
+    coordxy xx, coordxy yy,
+    struct permonst *mdat,
+    mmflags_nht entflags)
+{
+    return (enexto_core(cc, xx, yy, mdat, GP_CHECKSCARY | entflags)
+            || enexto_core(cc, xx, yy, mdat, entflags));
+}
+
 #ifdef NEW_ENEXTO
 
 boolean