Implement env(1) -0

-0 End each output line with NUL, not newline.

FreeBSD and GNU env(1) implement -0 which is used in 3rd party scripts.

This change is based on the FreeBSD code.

Add CVS Id tag and switch __attribute__ to __dead.

Implement env(1) -u

The option '-u name' causes removal of the name environment variable if
it is in the environment. This is similar to the unset command in sh(1).
The value for name must not include the '=' character.

Add HISTORY section in the man page.

The -u argument is implemented by Linux, FreeBSD and Darwin.
The lack of -u in NetBSD is a cause for a frequent fallout in the LLVM
toolchain test-suite.

minor KNF nits.

Do use putenv(3) to handle the provided strings directly, instead of
setenv(3) which need string splitting and later reassembly.

remove duplicate 'was' in a comment

Remove the \n and tabs from the __COPYRIGHT() strings.
Tweak to use a consistent format.

branches: 1.16.22;
de-__P, add ANSI prototypes, and a teeny bit of KNF.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22365, verified by myself.

fix nested extern

Don't declare 'extern opt*' getopt variables.

revert previous

remove superfluous '-' in getopt string

branches: 1.10.6;
WARNSify, fix .Nm usage

Include appropriate header files to bring prototypes into scope.
Removed explicit errno declarations.

Merge and Sync with 4.4BSD-Lite2
Mostly looks like the previous NetBSD version, actually -- only minimal
Lite2 stigmata preserved although I started with Lite2. Mostly the changes
were things like index->strchr and the rest was NetBSD code.

Provide prototypes in static function declarations.

POSIX.2 utilities must call setlocale(LC_ALL, "");

simplify error message handling by using err() function.

Minor tweaks: including header files to bring prototypes into scope,
explicitly declaring function return values, etc. to make gcc -Wall
shut up.

Add RCS identifiers.

Make Posix 1003.2 (Draft 11.2) compliant.

branches: 1.1.1;
Initial revision