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/allmain.c

@@ -201,6 +201,8 @@ moveloop(boolean resuming)
                     /* once-per-turn things go here */
                     /********************************/
 
+                    l_nhcore_call(NHCORE_MOVELOOP_TURN);
+
                     if (Glib)
                         glibr();
                     nh_timeout();
@@ -633,6 +635,8 @@ newgame(void)
                        * any artifacts */
     u_init();
 
+    l_nhcore_init();
+
 #ifndef NO_SIGNAL
     (void) signal(SIGINT, (SIG_RET_TYPE) done1);
 #endif
@@ -709,6 +713,8 @@ welcome(boolean new_game) /* false => restoring an old game */
                    : "%s %s, the%s %s %s, welcome back to NetHack!",
           Hello((struct monst *) 0), g.plname, buf, g.urace.adj,
           (currentgend && g.urole.name.f) ? g.urole.name.f : g.urole.name.m);
+
+    l_nhcore_call(new_game ? NHCORE_START_NEW_GAME : NHCORE_RESTORE_OLD_GAME);
 }
 
 #ifdef POSITIONBAR