Lua: improve level testing

Add des.finalize_level() used for testing in conjunction with
des.reset_level().
Add nhc.DLB to return 0 or 1 if DLB was defined at compile-time.
Change the test_lev.lua to give more informative messages instead of
just lua error when required file doesn't exist.
Add bigrm-11 to the level tests.

include/extern.h

@@ -1251,6 +1251,7 @@ extern void free_luathemes(boolean);
 extern void makecorridors(void);
 extern void add_door(int, int, struct mkroom *);
 extern void clear_level_structures(void);
+extern void level_finalize_topology(void);
 extern void mklev(void);
 #ifdef SPECIALIZATION
 extern void topologize(struct mkroom *, boolean));
@@ -2450,6 +2451,8 @@ extern void selection_do_ellipse(struct selectionvar *, int, int, int, int,
                                  int);
 extern void selection_do_gradient(struct selectionvar *, long, long, long,
                                   long, long, long, long, long);
+extern int lspo_reset_level(lua_State *);
+extern int lspo_finalize_level(lua_State *);
 extern void update_croom(void);
 extern const char *get_trapname_bytype(int);
 extern void l_register_des(lua_State *);

include/flag.h

@@ -173,6 +173,7 @@ struct instance_flags {
      * behaviour of various NetHack functions and probably warrant
      * a structure of their own elsewhere some day.
      */
+    boolean lua_testing;   /* doing lua tests */
     boolean debug_fuzzer;  /* fuzz testing */
     boolean in_lua;        /* executing a lua script */
     boolean defer_plname;  /* X11 hack: askname() might not set g.plname */