Add level flag for plane of fire fumaroles

Also reduce the size of the gas clouds.

Breaks saves and bones.

src/sp_lev.c

@@ -3747,6 +3747,8 @@ lspo_level_flags(lua_State *L)
             gl.level.flags.deathdrops = 0;
         else if (!strcmpi(s, "noautosearch"))
             gl.level.flags.noautosearch = 1;
+        else if (!strcmpi(s, "fumaroles"))
+            gl.level.flags.fumaroles = 1;
         else {
             char buf[BUFSZ];
             Sprintf(buf, "Unknown level flag %s", s);