Allow defining random-teleport exclusion zones in lua

Adds a new lua command

  des.exclusion({ type = "teleport", region = { x1,y1, x2,y2 } });

which allows defining "exclusion zones" in the level, areas where
random teleports (or falling into the level) will never place the hero.
Does not prevent targeted teleportation into the area.

Breaks saves and bones.

src/sp_lev.c

@@ -141,6 +141,7 @@ int lspo_ladder(lua_State *);
 int lspo_level_flags(lua_State *);
 int lspo_level_init(lua_State *);
 int lspo_levregion(lua_State *);
+int lspo_exclusion(lua_State *);
 int lspo_map(lua_State *);
 int lspo_mazewalk(lua_State *);
 int lspo_message(lua_State *);
@@ -6073,6 +6074,35 @@ lspo_levregion(lua_State *L)
     return 0;
 }
 
+/* exclusion({ type = "teleport", region = { x1,y1, x2,y2 } }); */
+int
+lspo_exclusion(lua_State *L)
+{
+    static const char *const ez_types[] = {
+        "teleport", "teleport-up", "teleport-down", NULL
+    };
+    static const int ez_types2i[] = {
+        LR_TELE, LR_UPTELE, LR_DOWNTELE, 0
+    };
+    struct exclusion_zone *ez = (struct exclusion_zone *) alloc(sizeof *ez);
+    lua_Integer x1,y1,x2,y2;
+
+    create_des_coder();
+    lcheck_param_table(L);
+    ez->zonetype = ez_types2i[get_table_option(L, "type", "teleport",
+                                                      ez_types)];
+    get_table_region(L, "region", &x1, &y1, &x2, &y2, FALSE);
+    ez->lx = x1;
+    ez->ly = y1;
+    ez->hx = x2;
+    ez->hy = y2;
+    cvt_to_abscoord(&ez->lx, &ez->ly);
+    cvt_to_abscoord(&ez->hx, &ez->hy);
+    ez->next = ge.exclusion_zones;
+    ge.exclusion_zones = ez;
+    return 0;
+}
+
 static void
 sel_set_lit(coordxy x, coordxy y, genericptr_t arg)
 {
@@ -6960,6 +6990,7 @@ static const struct luaL_Reg nhl_functions[] = {
     { "drawbridge", lspo_drawbridge },
     { "region", lspo_region },
     { "levregion", lspo_levregion },
+    { "exclusion", lspo_exclusion },
     { "wallify", lspo_wallify },
     { "wall_property", lspo_wall_property },
     { "non_diggable", lspo_non_diggable },