cmirrord now returns log name to kernel in CTR so it can be registered

cmirrord now returns log name to kernel in CTR so it can be registered

Version 2 of the userspace log protocol accepts return information during the
DM_ULOG_CTR exchange.  The return information contains the name of the log
device that is being used (if there is one).  The kernel can then register the
device via 'dm_get_device'.  Amoung other things, this allows for userspace to
assemble a correct dependency tree of devices - critical for LVM handling of
suspend/resume calls.

Also, update dm-log-userspace.h to match the kernel header associated with
this protocol change.  (Includes a version inc.)