Welcome back Big Endian, haven't seen you since the early 1990s!

Hack support for big-endian. It appears to work, but I stopped testing
when we found out the HP moonshot ARM cartridges are little-endian.

The approach here is that little-endian is the "native" imagezip format.
This makes backward compat easy and works most efficiently for the common
(still 100%) case of little-endian machines.

For frisbee, little-endian is also the default on-wire format...except
for the master server protocol which properly uses network order.
That should be fixed, but will require a version bump.

This stuff will likely get pulled into the main branch when the next
major version happens. RSN.