Use upstream Lua fix.

Author: tritao

contrib/lua/src/lundump.c

@@ -234,7 +234,7 @@ static void fchecksize (LoadState *S, size_t size, const char *tname) {
 #define checksize(S,t)	fchecksize(S,sizeof(t),#t)
 
 static void checkHeader (LoadState *S) {
-  checkliteral(S, (const char*)LUA_SIGNATURE + 1, "not a");  /* 1st char already checked */
+  checkliteral(S, &LUA_SIGNATURE[1], "not a");  /* 1st char already checked */
   if (LoadByte(S) != LUAC_VERSION)
     error(S, "version mismatch in");
   if (LoadByte(S) != LUAC_FORMAT)