Short strings always use all bytes in the hash

Collisions in short strings occurr just by their existence, when
internalizing them. (Collisions in long strings is caused/controlled
by the program, when adding them as keys to the same table.)

lstate.c

@@ -76,7 +76,7 @@ static unsigned int luai_makeseed (lua_State *L) {
   addbuff(buff, p, &h);  /* local variable */
   addbuff(buff, p, &lua_newstate);  /* public function */
   lua_assert(p == sizeof(buff));
-  return luaS_hash(buff, p, h);
+  return luaS_hash(buff, p, h, 1);
 }
 
 #endif