Lua: nhcore script with function callbacks

Adds possible callbacks for "start_new_game", "restore_old_game",
"moveloop_turn", and "game_exit" which when defined, will be called
from core code at the appropriate time.

Adds lua hooks for dump_fmtstr (only if DUMPLOG), dnum_name, u.moves,
u.uhave_amulet, and u.depth.

src/end.c

@@ -1753,6 +1753,8 @@ void
 nh_terminate(int status)
 {
     g.program_state.in_moveloop = 0; /* won't be returning to normal play */
+
+    l_nhcore_call(NHCORE_GAME_EXIT);
 #ifdef MAC
     getreturn("to exit");
 #endif
@@ -1761,6 +1763,7 @@ nh_terminate(int status)
     if (!g.program_state.panicking) {
         freedynamicdata();
         dlb_cleanup();
+        l_nhcore_done();
     }
 
 #ifdef VMS