MFC r193273: Fix segfault when giving invalid long option to pkg_info.

PR:		bin/133473
Submitted by:	Rafal Grodzinski
Approved by:	ed (mentor)
MFC r193524: do not force the mtu to 2290
merge r176058: more missing namespace wrappers for libthr
merge r180982,r181044,r181059,r181065,r181341,r183021: WARNS cleanup,
add thr_pread_{int,long,ptr} and thr_pwrite_{int,long,ptr}, and change
definition of psaddr_t (no impact on ABI).  Discussed with marcel@, but
any screwups are my own.
merge r180815,184081-184088,184091-184094,184634,184676-184677, 185277,
93589,193591: style and warning cleanups, libutil is now WARNS=6 clean.
Also merged setclasscpumask(), which would have been a b***h to isolate
from the rest of the changes.  AFAICT, nobody uses it anyway.
merge r181651, r193826: avoid writing an int to a char *.
merge r173718: reduce WARNS due to too many "variable might be clobbered
by longjmp" false positives.
merge r174111, r174112, r174335: style and warning fixes.  The functional
parts of these commits have already been merged.
Re-add accidentally removed code from the previous MFCs.
MFC fstat support bits for ZFS

Submitted by:	Alexander Nedotsukov
- enable building of loader by default
- fix MK_ZFS == "no" and MK_CDDL == "no" handling
Should be ${MK_ZFS} != "no"
MFC: r192432: Fail pwd_mkdb -C if the user name is MAXLOGNAME or longer.
fix loader for default settings case
Prevent integer overflow in direct pipe write code from circumventing
virtual-to-physical page lookups. [09:09]

Add missing permissions check for SIOCSIFINFO_IN6 ioctl. [09:10]

Fix buffer overflow in "autokey" negotiation in ntpd(8). [09:11]

Approved by:	so (cperciva)
Approved by:	re (not really, but SVN wants this...)
Security:	FreeBSD-SA-09:09.pipe
Security:	FreeBSD-SA-09:10.ipv6
Security:	FreeBSD-SA-09:11.ntpd
MFC r185647;
Several threads in a process may do vfork() simultaneously. Then, all
parent threads sleep on the parent' struct proc until corresponding
child releases the vmspace. Each sleep is interlocked with proc mutex of
the child, that triggers assertion in the sleepq_add(). The assertion
requires that at any time, all simultaneous sleepers for the channel use
the same interlock.

Silent the assertion by using conditional variable allocated in the
child. Broadcast the variable event on exec() and exit().

MFC r188750:
Adapt linux emulation to use cv for vfork wait.
merge r176055, r176056: use libc's version definition file.
merge r176060, r176071: add pthread_mutex_isowned_np() (already in libthr)
merge r173764: fix aliasing violations.
merge r173722: lower WARNS; we can't easily fix the (contrib) code.