Don't pass null kmdp to preload_search_info

On Xen PVH guests kmdp == NULL.

Submitted by:	royger
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
rewind: always clear error indicator.

Required by POSIX:
http://pubs.opengroup.org/onlinepubs/009695399/functions/rewind.html

Obtained from:	Apple Inc. (Libc 997.90.3)
MFC after:	1 week
ftello: return 1 when seeking offset on an append stream.

Obtained from:	Apple Inc. (Libc 997.90.3)
Phabric:	D442
MFC after:	2 weeks
Mostly cosmetic cleanups.

In fputs() avoid implcit casting on iov.iov_len.

MFC after:	3 days
In r264504, we prevented doing I/O for more than MAXPHYS by making
the assumption that consumers would respect bio_completed and/or
bio_resid to detect short reads. This assumption proved false and
file corruption was the result.
Create as many bios as we need to satisfy the original request.
Check the cached chunk every time we need to do I/O to increase the
hit rate.

Obtained from:	junipre Networks, Inc.
MFC after:	1 week
Revert	r268984:
Check for __SAPP flag before calling sflush.   This avoids
performance degradation compared to the previous approach.

Submitted by:	ache
MFC after:	2 weeks
Grammar and spelling fixes.
Add missing newline to an error message.

MFC after:	3 days
Cleanup the definition of two structures which are
exposed to userland. Therefore no MFC.
Checking for __SAPP alone is not enough because it is emulated O_APPEND
only, so works for only special fdopen() case. Add real O_APPEND too.
Back the whole change out until I figure out how to obtain O_APPEND,
it can't be used in this field at all.
Fix EABI unwind function declarations to match the function definitions.
The mismatch was noticed by clang, when using it to compile the in-tree
gcc and libstdc++.
Add FreeBSD to the list of environments that needs to handle R_ARM_TARGET2
relocations in unwind data as pc-relative indirect references.

MFC after:	1 week
s/PCBGROUPS/PCBGROUP/ manpage to match "options PCBGROUP".
Re-sort synopsis, add includes.
For "a"-mode files and rewind/fseek + fwrite combination return meaningful
value now, like Apple does, but avoid their __sflush physical write
performance degradation as much as possible.
/usr/bin/sendbug and the sendbug(1) man page were part of send-pr and
are no longer installed since r267486.  Add them to ObsoleteFiles.inc1,
which should have been done in r267486.

PR:		192010
Submitted by:	Vick Khera
Pointyhat to:	gavin
MFC after:	3 days
Add example script `add_some_packages.sh', demonstrating how to install
a list of packages using the bsdconfig(8) API, providing dialog(8) based
user experience (versus plain console output were you to use pkg(8)
directly to install the same list of packages).

Remove example script `browse_packages_ftp.sh', made obsolete because
the digests.txz and packagesite.txz databases for pkg(8) are not
available via FTP (HTTP only to pkg.freebsd.org SRV hosts).

Update example script `browse_packages_http.sh', made to work with new
pkg(8) demonstrating how to generate a local package repository.

Fix a bug in `bsdconfig packages' where packages were listed twice. This
fix requires pkg(8) version 1.2.7_4 or higher.

NB: It is the introduction of pkg(8) 1.2.7_4 wherein I am also able to
drastically reduce the generation time of package dependencies prior to
the dialog display (by utilizing the new `-I' flag to pkg-rquery(8)).

While here, fix a positional argument nit for f_index_initialize() of
`packages/index.subr' include (the one and only argument is positional
argument 1 to state the by-ref handle, indicating the variable to set
in the caller's namespace; the nit I'm fixing here is that we were
querying positional argument 2 for this information incorrectly; caused
by a missing hunk back around SVN r257795).

Fix a bug in sysrc(8) described by PR bin/187458 "sysrc(8) silently and
unexpectedly bootstraps pkg". This was caused by an explicit entry in
`/usr/share/bsdconfig/common.subr' (used by sysrc(8)) that called pkg(8)
to populate the $PKG_ABI global (called in a way that allows implicit
bootstrap of pkg(8)). The solution to which was to find every place in
bsdconfig(8) that requires the $PKG_ABI global and add a layer of
protection by way of introducing the new API call f_musthavepkg_init()
(provided by new include, `/usr/share/bsdconfig/packages/musthavepkg.subr'
intented to mirror `/usr/share/bsdconfig/mustberoot.subr'). When the
$PKG_ABI global is required, you can use `f_musthavepkg_init' to cause
graceful premature termination in the event that pkg(8) has not yet been
bootstrapped, and thus cannot be used to populate $PKG_ABI.

NB: If running interactively ($nonInteractive is NULL or unset), the
f_musthavepkg_init() API call will attempt to bootstrap pkg(8), but only
if the user chooses "Yes" to a Yes/No dialog confirming it is ok to
bootstrap.

While here, simplify an if-conditional in `media/http.subr' include to
use sh(1) inline assignment-with-break.

Also, fix a bug in `media/http.subr' and `media/httpproxy.subr' wherein
the error messages for various HTTP failures were not finding their way
to the console (needed to pass stdout to pass-thru descriptor).

While here, remove the executable bit from `packages/categories.subr',
`packages/index.subr', and `packages/packages.subr' includes.

Fix issues where pkg(8) complains about PACKAGESITE being defined.
Previously, we would set $PACKAGESITE and export it. Now we only set
$PACKAGESITE for invocations of "pkg update" -- getting rid of all the
spurious warnings about PACKAGESITE being deprecated (it's still used
in the case of "pkg update" for simplicity versus having to configure
a config-file).

Remove the leading argument from invocations of f_index_initialize() in
`packages/packages.subr' include. The leading argument no longer means
what it used to, pre SVN r257995).

PR:		bin/187458
Reviewed by:	nwhitehorn
MFC after:	1 week
X-MFC-to:	stable/10, stable/9
Avoid possible cast degradation.

For consistency with r268985 for fputs.c, assign iov_len
first, avoiding the cast to uio_resid (int in stdio)
from degrading the value.

We currently don't support lengths higher than INT_MAX so
this change is little more than cosmetic.

MFC after:	3 days