libc string functions were not ported from pwb to v7

https://minnie.tuhs.org/pipermail/tuhs/2017-August/011807.html

ok schwarze@

Use somewhat harsher language and better examples; demonstrate that
non-dangerous use functions is difficult.
ok guenther

Split out strncpy and strncat from strcpy and strcat manuals.
Requested by deraadt@

According to POSIX, if the src and dst strings overlap, the behavior
is undefined. Add a warning to that effect. OK deraadt@ jmc@

more library history
facts checked by sobrado@
style tweaks and ok jmc@

Use the fancy .In macro for includes. From Jan Klemkow. ok jmc schwarze

update HISTORY and SEE ALSO for all of string(3), together with various
smaller improvements; jmc@ and nicm@ both ask me to get this in because
further tweaking will be easier in-tree

convert to new .Dd format;

- macro, punctuation, and rewording tweaks
- avoid first person.

ok jmc

Be correct in our man pages when talking about NUL termination (that is,
termination with '\0') vs. null termination.
Input from krw@, jaredy@, jmc@. OK deraadt@

Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.

For strncpy(), dst is not NUL terminated if strlen(src) >= len.
Also fix a typo; adapted from a patch by Moritz Jodeit

Flesh out libc string function man pages.

repairs

some NAME section cleanup

some repairs, add example to strdup(3) page

remove argument from .Os macros so value in /usr/share/tmac/mdoc/doc-common
is used instead; kwesterback@home.com

typo

better examples section wrt strncpy()

.Xr strlcat, strlcpy

Fix RCS ids
Make sure everything uses {SYS,}LIBC_SCCS properly

initial import of NetBSD tree