MFC r271664:
  Cache GELI passphrases entered at the console during the boot process,
  in order to improve user-friendliness when a system has multiple disks
  encrypted using the same passphrase.

Relnotes:	yes
Approved by:	re (gjb)
Document r271470, addition of BIOS- and UEFI-capable CDROM images.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Document r271816, drm/i915 HW context support.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Add sponsor attribution for r271470

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Document r271967, mkimg(1) empty partition support.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Document r272006, GEOM_ELI passphrase caching on boot with multiple
providers.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Merge remote-tracking branch 'freebsd/stable/10' into hardened/10/aslr