Instalando un open source de un juego me han salido que me faltan estas cosas...  y no se ahora que hacer. alguien me puede explicar como ponerlas?

• No known PHP Accelerators werre detected. A PHP Accelerator is highly recommended, because it can grately improve the game performance.
• Multibyte String extension is mission. This extension provies UNICODE support for the game. It must be installed in order to continue.
• BZip2 extension is missing. This extension should be installed if you want to use .bz2 compressed game package archives. However you can continue the installation of the game.
• MemCache extension not found. Memory caching will be disabled.
  It is highly recommended to mount the /engine/data/cache folder under a RAM filesystem!(16Mb should be enough)

Errors where detected in the pre-installation check. Make sure to correct them before continuing

MUCHAS GRACIAS DE ANTEMANO

Pues si mal no recuerdo la extension critica MBstring debe ser activada por el administrador de miarroba, por lo que no puedes hacer nada.