systems: good old A20 gate was not properly enabled on all hardware. Even if it's not perfect now, either, it seems to work on many more systems (all I have access to, anyway). Please report if you have any issues with the 0x92 port A20 gate method. git-svn-id: file:///srv/svn/repos/haiku/trunk/current@11196 a95241bf-73f2-0310-859d-f6bbb57e9c96