Change to using device drivers for null, zero and digit Small changes to the way we init devices. NB the random driver has shown that devices are not being handled correctly, so this is something we'll ahve to live with until the vfs person fixes it. git-svn-id: file:///srv/svn/repos/haiku/trunk/current@148 a95241bf-73f2-0310-859d-f6bbb57e9c96