Factor interface list to its own command:

- Add handle_interface_list_command, used by handle_interface_command.
- Display output of new list to command console.
- Change first index of displayed drivers to 1; it's only cosmetic.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2129 b42882b7-edfa-0310-969c-e2dbd0fdcd60