* The device interface list now uses class DoublyLinkedList instead of struct list.
* Implemented SIOC[SG]IFMEDIA for setting (not supported by any device yet), and
retrieving the device media information.
* Fixed a locking bug in list_domain_interfaces().
* Added new stack function device_link_changed() that should be called in case the
link state (media) changed.
* The ethernet device module now spawns a thread and will periodically check the media
state of all ethernet devices that support this (if any).
* Minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20546 a95241bf-73f2-0310-859d-f6bbb57e9c96
