MFC r267921, r267934, r267949, r267959,	r267966, r268202, r268276,
    r268427, r268428, r268521, r268638,	r268639, r268701, r268777,
    r268889, r268922, r269008, r269042,	r269043, r269080, r269094,
    r269108, r269109, r269281, r269317,	r269700, r269896, r269962,
    r269989.

Catch bhyve up to CURRENT.

Lightly tested with FreeBSD i386/amd64,	Linux i386/amd64, and
OpenBSD/amd64. Still resolving an	issue with OpenBSD/i386.

Many thanks to jhb@ for	all the	hard work on the prior MFCs !

r267921 - support the "mov r/m8, imm8" instruction
r267934 - document options
r267949 - set DMI vers/date to fixed values
r267959 - doc: sort cmd flags
r267966 - EPT misconf post-mortem info
r268202 - use correct flag for event index
r268276 - 64-bit virtio capability api
r268427 - invalidate guest TLB when cr3 is updated, needed for TSS
r268428 - identify vcpu's operating mode
r268521 - use correct offset in guest logical-to-linear translation
r268638 - chs value
r268639 - chs fake values
r268701 - instr emul operand/address size override prefix support
r268777 - emulation for legacy x86 task switching
r268889 - nested exception support
r268922 - fix INVARIANTS build
r269008 - emulate instructions found in the OpenBSD/i386 5.5 kernel
r269042 - fix fault injection
r269043 - Reduce VMEXIT_RESTARTs in task_switch.c
r269080 - fix issues in PUSH emulation
r269094 - simplify return values from the inout handlers
r269108 - don't return -1 from the push emulation handler
r269109 - avoid permanent sleep in vm_handle_hlt()
r269281 - list VT-x features in base kernel dmesg
r269317 - Mark AHCI fatal errors as not completed
r269700 - Support PCI extended config space in bhyve
r269896 - Minor cleanup
r269962 - use max guest memory when creating IOMMU domain
r269989 - fix interrupt mode names