obvious .Pa fixes; found with mandocdb(8)

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

convert to new .Dd format;

Clarify the return value and drop nonapplicable bugs section hastily pasted
from ttyname(3).
Feedback espie@ jmc@, ok deraadt@ jmc@

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rescinded 22 July 1999.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

Various repairs, mostly to get rid of short lines.

After some constructive criticism from pjanzen@ and some e-mail tag:

- only use the .Dv NULL form when referring explicitly to a function
argument or return value
- otherwise, use these forms:
o non-null
o null-terminated (hyphenated form for predicate adjective)
o else, null terminated, or null terminate, whichever the case
o null pointer, null byte, null string, etc.
- may use NUL to refer to an ASCII NUL, but it doesn't need a .Tn macro

In general, capitalizing the word "null" everywhere is unnecessary and makes
the man pages harder to read. The above is consistent with popular programming
texts (i.e., K&R, Stevens).

repairs

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

branches: 1.1.1;
Initial revision