MFC r297790:
r297790 (by pfg):

libc: replace 0 with NULL for pointers.

While here also cleanup some surrounding code; particularly
drop some malloc() casts.

Found with devel/coccinelle.

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

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

Avoid NULL deference which causes DEBUG1 to crash, not to print useful
information.

Obtained from: OpenBSD

- Avoid overwriting the cursor page when the cursor page becomes the
LRU page.
- Fix for sequential retrieval failure when using large key/data pairs.

Obtained from: OpenBSD

When allocating memory, zero out them if we don't intend to overwrite them
all; before freeing memory, zero out them before we release it as free
heap. This will eliminate some potential information leak issue.

While there, remove the PURIFY option. There is a slight difference between
the new behavior and the old -DPURIFY behavior, with the latter initializes
memory with 0xff's. The difference between old and new approach does not
generate observable difference.

Obtained from: OpenBSD (partly).

Diff reduction against OpenBSD: ANSI'fy prototypes.

(This is part of a larger changeset which is intended to reduce diff only,
thus some prototypes were left intact since they will be changed in the
future).

Verified with: md5(1)

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

Remove __P() usage.

Remove 'register' keyword.

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

Back out most of the last backout. :-) Guido removed the 1.1.1.1->1.1.1.2
changes from the vendor branch as well, backing the db-1.82 changes.

This file should now be the same as it was in rev 1.1.1.2.

Backout bzero patch.

Somehow, I also managed to get quite some other changes in this file at
the same time. All I did was checkout the file and made a single change.
If someone has an explanation how these PURIFFY defines got in...

When freeing buffers in the db routines, also zeroize them
This should solve the bug where a coredumping ftpd reveals
encrypted passwords.
Obtained from: OpenBSD

This commit was generated by cvs2svn to compensate for changes in r14272,
which included commits to RCS files with non-trunk default branches.

Import updated Berkeley DB into CSRG branch

BSD 4.4 Lite Lib Sources