libc/<arch>/sys/Makefile.inc -> libsys/<arch>/Makefile.sys.

Require that libsys/<arch>/Makefile.sys exist.  At least for current
archtiectures, it's not possible for an architecture to not have and MD
syscall bits.

powerpcspe/Makefile.sys's structure means it had to be modified when moved
so rename detection won't work, but it has trivial contents so the
history is unimportant.

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths to allow libc to find them in their new home.

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

Add a _SYSCALL(name) which calls the SYS_name syscall.  Use it to add a
_SYSCALL_BODY() macro which invokes the syscall and calls cerror as
required.  Use the latter to implement PSEUDO() and RSYSCALL().

Reviewed by:	imp, markj
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D43059

For architectures where vfork.S was named Ovfork.S this was needed, but
it was always pointless here as an entry in either MDASM or NOASM is
equivalent.

Reviewed by:	kib
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42914

Both system calls were stubs returning EOPNOTSUPP and libc did not
provide _ or __sys_ prefixed symbols.  The actual implementation of
sbrk(2) is on top of the undocumented break(2) system call.

Technically this is a change in ABI, but no non-contrived program ever
called these syscalls.

Reviewed by:	kib, emaste
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42872

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by:		Netflix

Remove stray blank lines left over from $FreeBSD$ removal as well as
some CVS-era (perhaps pre-repocopy) version comments.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D42611

These sys/cdefs.h are not needed. Purge them. They are mostly left-over
from the $FreeBSD$ removal. A few in libc are still required for macros
that cdefs.h defines. Keep those.

Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D42385

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/