Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r256343,256540-256541,256544,256549,256551,256553,257939,258021,258927,
259144,259148,259470,259472,259474,259476-259478,259480-259481,259570,
259597-259598, and 261960 (24 revisions; summarized below)...
r256343: Add zfsboot module as an option for automatic configuration
r256540: Add zpool_cache_* variables to loader.conf(5)
r256541: Document BSDINSTALL_TMPBOOT in bsdinstall.8
r256544: Fix a typo when setting up loader.conf(5) GELI entries
r256549: Document zfsboot in bsdinstall.8
r256551: Bump .Dd date in bsdinstall.8
r256553: Align ZFSBOOT_BEROOT_NAME with sysutils/beadm + Solaris beadm
r257939: Validate scripted partition entry before acting on disks
r258021: Switch default MBR bootcode from /boot/boot0 to /boot/mbr
r258927: Fix early regression in enabling the Encryption feature
r259144: Fix early regression in entering passphrase for Encryption
r259148: Fix typo that broke booting from Encrypted setup
r259470: Add default /var/mail with atime=on for mail apps
r259472: Accept NULL input as also meaning zero swap
r259474: Bug fixes and debugging improvements
r259476: Improve default ZFS disk layout
r259477: fletcher4 is currently the default
r259478: De-uglify the geli(8)-setup infobox by adding a newline
r259480: Fix ghosted zroot pool issue
r259481: Auto-enable 4k alignment with Encryption
r259570: Fix "[: -eq: argument expected" error
r259597: Fix installation to 3-4+ disks
r259598: Set the cachefile property so bootpools get imported
r261960: Add zfsboot to scripted interface of bsdinstall

MFC revisions 230804,254265,255908,256338,256345,256347-256348,256489,
257842-257845,257872,259115,259143,259276,259468-259469,259572,259686,
260260-260262,260866, and 260900 (25 revisions; summarized below)...
r230804: Fix a whitespace nit (kevlo)
r254265: (recording mergeinfo only)
r255908: Remove the is (Iceland) mirror per mail from the admins (brd)
r256338: Dump 4096 bytes from /dev/random to /entropy (des)
r256345: Rewrite the keymap module
r256347: Detect when an interface is wireless (Warren Block)
r256348: Merge dumpdev into regular services; enable (Allan Jude)
r256489: Add executable bit to docsinstall and entropy scripts
r257842: Performance and debugging enhancements
r257843: Remove ttys(5) munging from previous commit
r257844: Copy install log to deployed /var/log for debugging
r257845: Fixup to last commit
r257872: Doc fixup -- add missing .El (joel)
r259115: Prevent log file from becoming truncated
r259143: Use sed(1) /i instead of /I (eadler)
r259276: Fix `local: Not in a function' error in logfile
r259468: Ignore mouse-release command from VMware
r259469: Mask error from newaliases(1) when hostname not fully qualified
r259572: Fix `rm: /tmp/bsdinstall_etc/fstab: ..." error in logfile
r259686: Move VMware mouse-release solution
r260260: Remove what appears to be a stray debugging printf
r260261: Lower priority of open wireless access policy (gavin)
r260262: Allow bsdinstall to use WPA-Enterprise networks (gavin)
r260866: Fix bad comparison and fix file comment (Christoph Mallon)
r260900: Whitespace and style nits

MFC miscellaneous bug fixes (r228042,228192,230522,232531,233473,233904,
235228,239500,241902,242188,243832,243854,244858,245333). This is mostly
documentation fixes and updates to the default FTP list that got left
behind in -CURRENT.

MFC r228194:

Prevent user astonishment by providing the shell option at the end, after
any installer-provided configuration files have been copied. This allows
users to edit their fstab, if desired, and to see what the installer has
placed in rc.conf.

Requested by: phk
Approved by: re (kensmith)

MFC r226507:
> Escape the newline so we get a proper line continuation. Without this
> the text of the menu selections doesn't get displayed properly and it
> makes the installer appear to lock up for no obvious reason.
>
> Reviewed by: nwhitehorn

Insta-MFC being done because 9.0-RC1 builds are being held for this.

Approved by: re (kib, bz)

MFC r226059:
Move "Exit" to the first entry in the list, so that it is the default
choice.

PR: bin/160913
Approved by: re (kib)

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Inquire about terminal type if starting from a serial console and do
not configure the host's networking if netbooted [1]. Also fix FTP
installations behind some firewalls [2].

PR: bin/159583 [2]
Reported by: stas [1]
Approved by: re (kib)

Per request of the docs team, install docs as packages, instead of via
the normal distfile mechanism. Thanks to Marc Fonvieille for the patch and
for putting up with me taking entirely too long to commit this!

Submitted by: blackend

Fix opening a shell on the new system (prevent the shell's stderr from
ending up in the install log).

Fix shell-based partitioning.

Fix mirror selection, which was broken by stderr redirection.

Reported by: Garrett Cooper

Rename the "Reboot" option to "Exit", which reflects what it actually
does. The rc.local wrapper script will also soon grow an option to use the
live environment after installation, so an immediate reboot isn't even
necessarily implied.

Committing while tired is never a good idea. Remove an unconditional error
exit left over from debugging.

Improve error handling.

Add mirror selection for FTP installs. To support TBEMD installs
(e.g. powerpc64), this looks in a slightly different default path than now,
specifying both $MACHINE and $MACHINE_ARCH:
MIRROR/pub/FreeBSD/releases/`uname -p`/`uname -m`/`uname -r`

How to handle TBEMD properly probably merits some more discussion, but,
since no such 9.0-CURRENT distfiles exist at the moment, all existing
mirrors presently fail anyway.

Add generation of an installation manifest containing SHA256 checksums as
well as package descriptions and add code in the installer to check the
checksums.

Correct typo.

Make installations work when no optional components are selected.

Add support for optional distributions, installation of the ports tree and
src. Fitting all of this on a single CD along with a full system requires
changing the default compression algorithm from gzip to xz.

Import bsdinstall. This is meant to be (eventually in conjunction with
pc-sysinstall) a replacement for sysinstall in the 9.0 release and beyond.
Currently supported platforms are sparc64, pc98, i386, amd64, powerpc, and
powerpc64. Integration into the build system will occur in the coming
weeks.

Merging with pc-sysinstall will use this code as a frontend, while
temporarily retaining the interactive partition editor here. This work
will be done in parallel with improvements on this code and release
integration.

Thanks to all who have provided testing and comments!