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

1 files changed, 12 insertions, 4 deletions

diff --git a/lib/libc/gen/_spinlock_stub.c b/lib/libc/gen/_spinlock_stub.c
index e3a800d..071fc20 100644
--- a/lib/libc/gen/_spinlock_stub.c
+++ b/lib/libc/gen/_spinlock_stub.c
@@ -35,18 +35,27 @@
 
 #include <stdio.h>
 
-/* Don't build these stubs into libc_r: */
-#ifndef	_THREAD_SAFE
 #include "spinlock.h"
 
 /*
- * Declare weak references in case the application is not linked
+ * Declare weak definitions in case the application is not linked
  * with libpthread.
  */
+#pragma weak _atomic_lock=_atomic_lock_stub
 #pragma weak _spinlock=_spinlock_stub
 #pragma weak _spinlock_debug=_spinlock_debug_stub
 
 /*
+ * This function is a stub for the _atomic_lock function in libpthread.
+ */
+long
+_atomic_lock_stub(volatile long *lck)
+{
+	return (0L);
+}
+
+
+/*
  * This function is a stub for the spinlock function in libpthread.
  */
 void
@@ -61,4 +70,3 @@ void
 _spinlock_debug_stub(spinlock_t *lck, char *fname, int lineno)
 {
 }
-#endif