lua: disable memory accounting for luajit

This is a stopgap measure. In theory we could maybe poll the memory
usage on luajit, but for now, simply reverting this part of fd3caa26
makes Lua work again. (And we can still collect cpu usage metrics)

Proper solution pending (tm)

player/lua.c

@@ -159,6 +159,7 @@ static void steal_node_alloctions(void *tmp, mpv_node *node)
     talloc_steal(tmp, node_get_alloc(node));
 }
 
+#ifndef HAVE_LUAJIT
 // lua_Alloc compatible. Serves only to retrieve memory usage.
 static void *mp_lua_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
 {
@@ -182,6 +183,7 @@ static void *mp_lua_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
 
     return ptr;
 }
+#endif
 
 static struct script_ctx *get_ctx(lua_State *L)
 {
@@ -434,7 +436,12 @@ static int load_lua(struct mp_script_args *args)
         goto error_out;
     }
 
+#if HAVE_LUAJIT
+    // luajit forces the use of its internal allocator, at least on 64-bit
+    lua_State *L = ctx->state = luaL_newstate();
+#else
     lua_State *L = ctx->state = lua_newstate(mp_lua_alloc, ctx);
+#endif
     if (!L) {
         MP_FATAL(ctx, "Could not initialize Lua.\n");
         goto error_out;