Log Message:
emulators/simh: update to 2021.12.11, fixing a dhcp problem.

On a microvax 3900 with qt0 ethernet, dhcp did not work because
a) netbsd doesn't receive broadcasts on qt0 (unless promiscuous mode is set)
b) the dhcp reply was sent as a broadcast.
This update fixes b) which is under control of simh.

Changes since previous snapshot (new to old):

ETHER: Fix NAT dhcp behavior to properly respond to the MAC of the requestor
SCP, makefile: Rename build conditional HAVE_DLOPEN to SIM_HAVE_DLOPEN
SCP: Prefer Posix 'command -v' over 'which'
AltairZ80: Improved vector interrupt implementation
SCSI, VAX & PDP11: Force Read Only attach for CDROM  devices
SCP: Provide commit id information when archived simh content is used
H316: The UDP code doesn't need anything from h316_defs.h.
DISK: Properly allow/disallow containers of reasonable/unreasonavle sizes
DISK: Preserve container dates when adding or removing container meta data
FIO: Add support to set file access and modify times
makefile: Fix minor line ending inconsistencies
makefile: Support both .so and .a link libraries on Linux
FIO: Emit reasonable error message when shm_open() API isn't available locally
PDP8: Fix device conflict warnings to report problems correctly
3b2: Remove glibc-specific longjmp
TIMER: Be less aggressive to disable throttling after initial calibration
H316: Call the host interface TX service routine.
H316: Fix debugging host interface messages.
H316: Signal the host/IMP ready bits in the host interface.
H316: Fix reading messages from the host interface.
H316: Fix host interface word counts.