Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Turn off default generation of userland dot symbols on powerpc64 now that
we have a binutils that supports it. Kernel dot symbols remain on to assist
DDB.

The 64-bit PowerPC ABI implemented in binutils 2.15 requires some special
quirks for weak-symbol handling. Text symbols require also marking weak
the special dot-symbol associated with the function, and data symbols
require that you not do that. To fix this, provide a hacked
__weak_reference for powerpc64, and define a new __weak_reference_data
for the single weak data symbol in base.

Revert after: binutils 2.17 import
Obtained from: projects/ppc64

Add prototype for libc internal interfaces.

Fix SCM ID's.

To be consistent, use the __weak_reference macro from <sys/cdefs.h>
instead of #pragma weak to create weak definitions. This macro is
improperly named, though, since a weak definition is not the same
thing as a weak reference.

Suggested by: bde

Remove _THREAD_SAFE and make libc thread-safe by default by
adding (weak definitions to) stubs for some of the pthread
functions. If the threads library is linked in, the real
pthread functions will pulled in.

Use the following convention for system calls wrapped by the
threads library:
__sys_foo - actual system call
_foo - weak definition to __sys_foo
foo - weak definition to __sys_foo

Change all libc uses of system calls wrapped by the threads
library from foo to _foo. In order to define the prototypes
for _foo(), we introduce namespace.h and un-namespace.h
(suggested by bde). All files that need to reference these
system calls, should include namespace.h before any standard
includes, then include un-namespace.h after the standard
includes and before any local includes. <db.h> is an exception
and shouldn't be included in between namespace.h and
un-namespace.h namespace.h will define foo to _foo, and
un-namespace.h will undefine foo.

Try to eliminate some of the recursive calls to MT-safe
functions in libc/stdio in preparation for adding a mutex
to FILE. We have recursive mutexes, but would like to avoid
using them if possible.

Remove uneeded includes of <errno.h> from a few files.

Add $FreeBSD$ to a few files in order to pass commitprep.

Approved by: -arch