Added support for extra ifconfig args to jail ip4.addr & ip6.addr params

This allows for CARP interfaces to be  used in jails e.g.
ip4.addr = "em0|10.10.1.20/32 vhid 1 pass MyPass advskew 100"

Before this change using exec.prestart to configure a CARP address
would result in the wrong MAC being broadcast on startup as jail creates
IP aliases to support ip[4|6].addr before exec.prestart is executed.

PR:		191832
Reviewed by:	jamie
MFC after:	1 week
X-MFC-With:	r269340
Phabric:	D528
Sponsored by:	Multiplay
set EXT2_LINK_MAX to LINK_MAX

In linux EXT4_LINK_MAX is now 64000.  We can't really do that
since i_nlink and va_nlink are signed so setting higher values
is likely to cause trouble.

This is a system limitation so set the EXT_LINK_MAX to
what the system can handle.

MFC after:	3 days
Preserve the errno value of an ioctl before calling free(3). Previously,
errno was very occasionally being clobbered, resulting in a bogus error from
dt_consume() and thus an error from dtrace(1).

MFC after:	2 weeks
Return 0 for the PPID of threads in process 0, as process 0 doesn't have a
parent process.

MFC after:	2 weeks
Add a comment for easier code understanding.
Add support for the SCTP_RECONFIG_SUPPORTED and the corresponding
sysctl controlling the negotiation of the RE-CONFIG extension.

MFC after: 3 days
Bring in the latest standard defines for imx6 clocks referenced in dts files.
add xrefs for the other functions...

There should be more text in this page talking about each of these links,
but at least people know about them now...

MFC after:	1 week
fix misordering...

Obtained from:	gjb
MFC after:	1 week
Add support for multi-threading of soft updates.

Replace a single soft updates thread with a thread per FFS-filesystem
mount point. The threads are associated with the bufdaemon process.

Reviewed by:  kib
Tested by:    Peter Holm and Scott Long
MFC after:    2 weeks
Sponsored by: Netflix
Integrate lib/libmp into the build/kyua

- Remove the .t wrapper
- Fix -Wreturn-type warnings with clang

This change has been tested on amd64/i386

Phabric: D530
Reviewed by: jmmv
Approved by: jmmv (co-mentor)
MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division
cxgbe(4): Do not run any sleepable code in the SIOCSIFFLAGS handler when
IFF_PROMISC or IFF_ALLMULTI is being flipped.  bpf(4) holds its global
mutex around ifpromisc in at least the bpf_dtor path.

MFC after:	3 days
Remove unnecessary inclusions of bsd.own.mk.
Include the kernel options after bsd.init.mk so that when we're
compiling on older systems that define all the MK variables in
bsd.own.mk we don't get the multiply defined error for options that
live in both.
Move most of the 15 variations on generating opt_inet.h and
opt_inet6.h into kmod.mk by forcing almost everybody to eat the same
dogfood. While at it, consolidate the opt_bpf.h and opt_mroute.h
targets here too.
Merge from CheriBSD:

Make the sysinit tool a build tool rather than building in with
/usr/bin/cc and running it from OBJDIR.  (It will be moved to usr.bin
once a manpage is written and a few style cleanups are done.)

Split the makefile bits for Hans' kernel shim layer into their own
includable kshim.mk.

Move USB support into a .mk file so loaders can include it.
MFV r269542:

In vdev_get_stats, check that the vdev is not a hole before computing the
fragmentation.  This fixes a panic when removing log device.

Illumos issue:
    5049 panic when removing log device

Author:		Alex Reece <alex@delphix.com>
MFC after:	2 weeks
Revert r269523:

Providing a higher EXT2_LINK_MAX limit is a bad idea for ext2/3.

Discussed with:	bde
Check gethostname(2) return code - but even if it succeeds it may not
null terminate.

Temporarily use "From: $user@$hostname" rather than "From: $user".
The latter exposes incompatible behavior if using dma(8).  sendmail(8)
(and other alternatives) canonify either form on submission (even
if masquerading), but dma will leak a non-compliant address to
the internet.
Ensure we catch USB transfers which complete right away.