Fix inconsistent token parameters for kbd_allocate() and kbd_release() in vt(4).

PR:		191306
Submitted by:	jau789@gmail.com
Sponsored by:	The FreeBSD Foundation
The GNU readline library is now an INTERNALLIB - that is, it is
statically linked into consumers (GDB and variants) in the base
system, and the shared library is no longer installed.

That also allows ports to be able to use a modern version of readline

PR:		162948
Reviewed by:	emaste
Document r268461, readline(3) shlib no longer installed, and
statically linked into consumers in the base system.

Sponsored by:	The FreeBSD Foundation
In libproc, avoid calling __cxa_demangle(), and thus depending on either
libcxxrt or libsupc++, if WITHOUT_CXX is defined.

Noticed by:	sbruno
MFC after:	1 week
MFV r268452:

Explicitly mark file removal transactions as "presumed to result
in a net free of space" so they will not fail with ENOSPC.

Illumos issue:	4950 files sometimes can't be removed from a full
		filesystem
MFC after:	2 weeks
Current code in sysctl proc.vmmap, which intent is to calculate the
amount of resident pages, in fact calculates the amount of installed
pte entries in the region.  Resident pages which were not soft-faulted
yet are not counted.

Calculate the amount of resident pages by looking in the objects chain
backing the region.

Add a knob to disable the residency calculation at all.  For large
sparce regions, either previous or updated algorithm runs for too long
time, while several introspection tools do not need the (advisory) RSS
value at all.

PR:	kern/188911
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Implement sysconf(_SC_GETGR_R_SIZE_MAX) and sysconf(_SC_GETPW_R_SIZE_MAX).

Reported by:	Dmitry Sivachenko <trtrmitya@gmail.com>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
MFV r268453:

Diff reduction against Illumos.

MFC after:	 2 weeks
MFV r268454:

Refresh zpool list for each interval in order to produce fresh
output.

Illumos issue: 4966 zpool list iterator does not update output

MFC after:	 2 weeks
For safety, ensure that any consumer of the set_regs() and
ptrace_set_pc() use the correct return to userspace using iret.

The signal return, PT_CONTINUE (which in fact uses signal return path)
set the pcb flag already.  The setcontext(2) enforces iret return when
%rip is incorrect.  Due to this, the change is redundand, but is made
to ensure that no path which modifies context, forgets to set
PCB_FULL_IRET.

Inspired by:	CVE-2014-4699
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Should check fb_read method presence instead of double check for fb_write.

Pointed by:     emaste

Sponsored by:	The FreeBSD Foundation
MFV r268455:

Use reserved space for ZFS administrative commands.

We reserve 1/2^spa_slop_shift = 1/32 or 3.125% of pool space (or 32MB at
least) for system use.  Most ZPL operations, e.g. write(2), creat(2), will
fail with ENOSPC if we fall below this.

Certain operations, e.g. file removal and most administrative actions,
still permitted until half of the slop space is used.  This would allow
users to use these operations to free up space in the pool when pool is
close to full but half of slop space is still free.

A very restricted set of operations that frees up space or change quota
are always permitted, regardless of the amount of free space.

MFC after:	 2 weeks
Merge the clang support from i386. Don't move to clang yet.
Make SERIAL support optional again. Enable it for i386 because a huge
percentage of machines has a 16550. Disable it for pc98 since only a
tiny fraction of them have one. These changes save 293 bytes when
building with clang, but preserves the ability to build with serial if
you really want.  We now have 92 bytes free (412 with the in-tree gcc).
Compile boot2 with clang on pc98.
Now that pc98 no longer needs gcc to compile boot2, remove the special
case and treat it just like i386.