constraints on the rman and reject attempts to manage a region that is out
of range.
- Fix various places that set rm_end incorrectly (to ~0 or ~0u instead of
~0ul).
- To preserve existing behavior, change rman_init() to set rm_start and
rm_end to allow managing the full range (0 to ~0ul) if they are not set by
the caller when rman_init() is called.