was sent to developers, but will eventually become a man page or
something), i noticed a few in various names:
(1) _map and _alloc should take a flags argument, rather than a
'cacheable' boolean.
(2) BUS_BARRIER_* flags should be BUS_SPACE_BARRIER_*.
(3) bus_space_copy_* should be bus_space_copy_region_* for consistency
with other region ops.
Fix all of these (in a backward-compatible way, at least for now). Redefine
internal usees of those names to use the new names. Also, while at it,
clean up the copy functions (remove unnecessary variables) and make sure
that they and other functions conform to the spec.