MFC r256657,r257018,r257347,r257423,r257729,r257767,

MFC r256657,r257018,r257347,r257423,r257729,r257767,
    r257933,r258609,r258614,r258668,r258673,r258855

Pull in some minor bugfixes and functionality enhancements
from CURRENT. These are candidates to be moved to 10.0-release.

r258855
mdoc: quote string properly.

r258673
Don't create an initial value for the host filesystem of "/".

r258668
Allow bhyve and bhyveload to attach to tty devices.

r258614
The 22-bit Data Byte Count (DBC) field of a Physical Region Descriptor was
being read as a 32-bit quantity by the bhyve AHCI driver.

r258609
Fix discrepancy between the IOAPIC ID advertised by firmware tables and the
actual value read by the guest.

r257933
Route the legacy timer interrupt (IRQ0) to pin 2 of the IOAPIC.

r257767
Fix an off-by-one error when iterating over the emulated PCI BARs.

r257729
Add the VM name to the process name with setproctitle().

r257423
Make the virtual ioapic available unconditionally in a bhyve virtual machine.

r257347
Update copyright to include the author of the LPC bridge emulation code.

hand-merge r257018
Tidy usage messages for bhyve and bhyveload.

r256657
Add an option to bhyveload(8) that allows setting a loader environment variable
from the command line.

Discussed with:	neel

git-svn-id: svn://svn.freebsd.org/base/stable/10@259301 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f