Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Add pwcache(3) and vis(3) to libegacy as install(1) is about to grow a
dependency on them.

Sponsored by: DARPA, AFRL

r235638 is not the clean way to add support for building on ancient FreeBSD
versions. Instead use Imp's good work on "legacy" and follow the outcome
of the previous TRB discussions on this topic.

Now use the libc getline() if it exists, and only where it doesn't
create a bootstraping version.

Revert r227538, since it doesn't compile with clang at all (it doesn't
allow the built-in operations to be redefined, at least not without
excessive force).

Instead, just disable LLVM's support for atomic operations for now.
Nothing in either clang or the tablegen tools currently depends on it.

This still allows users of head built before r198344 to upgrade to
top-of-head seamlessly.

LLVM uses atomic operations, which are not supported on i386 and GCC
emits calls for them, rather than expanding them inline. Older FreeBSD
versions compile for i386 by default and as such we end up with
unresolved symbols when we build LLVM's TableGen utility as a build
tool on them. Add the functions that GCC emits here, but don't bother
to make them atomic. Such is not needed.

Submitted by: marcel
MFC after: 1 week

Remove 5.x and 6.x cruft - source upgrades to RELENG_8 from versions prior
to RELENG_7 are not supported.

Make <runefile.h> internal to libc.

Suggested by: phantom

Add hacks that I use to test cross-builds (by building on
native and foreign architectures and comparing products).
They eliminate most of the differences caused by different
object directory paths, timestamping, and identification.

(Note WORLDTMP was renamed to ${OBJTREE}${.CURDIR}/tmp.)

Bootstrap gencat(1).

OK'ed by: phantom

As threatened, drop support for source upgrades from pre-5.3.

Inspired by: obrien

Make the format of LC_CTYPE files architecture independent by
introducing the disk formats for _RuneLocale and friends.

The disk formats do not have (useless) pointers and have 32-bit
quantities instead of rune_t and long. (htonl(3) only works
with 32-bit quantities, so there's no loss).

Bootstrap mklocale(1) when necessary. (Bootstrapping from 4.x
would be trivial (verified), but we no longer provide pre-5.3
source upgrades and this is the first commit to actually break
it.)

Removed extraneous parentheses.

Add getopt_long.c if ${BOOTSTRAPPING} < 502104

Unbreak the upgrade path from 4.9 after removal of GNU getopt and
<gnuregex.h>.

A version of <sys/endian.h> in RELENG_4 doesn't have 64-bit functions.

Spotted by: simokawa

libc_gen/basename.c depends on include/libgen.h.

-legacy and /.../legacy/... looks better than build or bootstrap in
the logs, so use that instead.

Submitted by: obrien.

Migrate to a new way of dealing with building from old revisions of
FreeBSD. This method attempts to centralize all the necessary hacks
or work arounds in one of two places in the tree (src/Makefile.inc1
and src/tools/build). We build a small compatibility library
(libbuild.a) as well as selectively installing necessary include
files. We then include this directory when building host binaries.

This removes all the past release compatibilty hacks from various
places in the tree. We still build on tip of stable and current. I
will work with those that want to support more, although I anticipate
it will just work.

Many thanks to ru@, obrien@ and jhb@ for providing valuable input at
various stage of implementation, as well as for working together to
positively effect a change for the better.