If there's no video, do as we did before, otherwise route logs to the fb
driver instead. (Need to clean this up to just have a log consumer
general interface?) Also added a "scrollback" class to fb driver and
updated the system_get_log syscall.
2MiB large pages were being used for any large page mapping, but the
page manager doesn't correctly handle them everywhere yet. Now only
allow them for offset pointers (eg MMIO space) that will never be
unmapped.