* bb: cmdline history & tab completion

Signed-off-by: Dmitry Ponyatov <dponyatov@gmail.com>
* libc: + usleep for bb

Signed-off-by: Dmitry Ponyatov <dponyatov@gmail.com>
+ qemu

Signed-off-by: Dmitry Ponyatov <dponyatov@gmail.com>
* panic=0

Signed-off-by: Dmitry Ponyatov <dponyatov@gmail.com>