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)

sh: Fix duplicate prototypes for builtins.

Have mkbuiltins write the prototypes for the *cmd functions to builtins.h
instead of builtins.c and include builtins.h in more .c files instead of
duplicating prototypes for *cmd functions in other headers.

sh: On startup of the shell, use PWD from the environment if it is valid.
Unset PWD if it is incorrect and no value for it can be determined.
This preserves the logical current directory across shell invocations.

Example (assuming /home is a symlink):
$ cd
$ pwd
/home/foo
$ sh
$ pwd
/home/foo

Formerly the second pwd would show the physical path (symlinks resolved).

Remove clause 3 from the UCB licenses.

OK'ed by: imp, core

o __P has been reoved
o Old-style K&R declarations have been converted to new C89 style
o register has been removed
o prototype for main() has been removed (gcc3 makes it an error)
o int main(int argc, char *argv[]) is the preferred main definition.
o Attempt to not break style(9) conformance for declarations more than
they already are.
o Change
int
foo() {
...
to
int
foo(void)
{
...

$Id$ -> $FreeBSD$

Don't blindly eliminate `..' and the previous pathname component.
PR: 2541
Obtained from: NetBSD

Added $Id$.

Make sh(1) a little braver in the face of adversity. sh(1)
now handles the getpwd() init problem the same way as bash
and ksh do. Also while I was in here, I cleaned up the format
a little, removed some unnnecessary #if SYMLINKS cruft, and
changed the pwd builtin to use getcwd(3) as Joerg suggested.

Merge in NetBSD mods and -Wall cleaning.

Obtained from: NetBSD, me