Tell the client what objects are breakable so that Gauss Gun shots won't be visibly reflected

[Toodles2You]

This updates the "hack" to tell the client what objects are breakable glass by setting the pev->playerclass field. Constants have been defined to make it more clear what's going on. An extra bit is sent via delta.lst to flag objects as breakable and a check is performed in the weapon code for the Gauss Gun fire.