Propagate the error status of /usr/sbin/bhyve out of the vmrun.sh script.
Clean up the /dev/vmm entry for this VM when vmrun.sh exits.

Reviewed by: neel
Phabric:     D767
Implement range checks between UNMAP and READ/WRITE commands.

Before this change UNMAP completely blocked other I/Os while running.
Now it blocks only colliding ones, slowing down others only due to ZFS
locks collisions.

Sponsored by:	iXsystems, Inc.
Improve transmit sending offload, TSO, algorithm in general.

The current TSO limitation feature only takes the total number of
bytes in an mbuf chain into account and does not limit by the number
of mbufs in a chain. Some kinds of hardware is limited by two
factors. One is the fragment length and the second is the fragment
count. Both of these limits need to be taken into account when doing
TSO. Else some kinds of hardware might have to drop completely valid
mbuf chains because they cannot loaded into the given hardware's DMA
engine. The new way of doing TSO limitation has been made backwards
compatible as input from other FreeBSD developers and will use
defaults for values not set.

MFC after:	1 week
Sponsored by:	Mellanox Technologies
Add "readcache" and "writecache" LUN options to control default behavior.

Default values are "on".  Disabling requires backend to support IO_DIRECT
and IO_SYNC flags respectively, or some alternatives.
vt(4): Enclose vt_mouse_paste() prototype inside #ifndef SC_NO_CUTPASTE/#endif

This fixes the build with sparc64 LINT for instance.

Reported by:	bz@
MFC after:	3 days