panic.9: add xrefs to printf(3) and printf(9)

printf(3) fmt strings are referenced in the body, and there might as
well be a cross-reference to other kernel message output functions.

Retire ipkdb entirely. The option was removed from the config files
yesterday.

ok kamil christos

branches: 1.21.30; 1.21.32;
* decapitalize NAME section's line
* improve wording
* make RETURN VALUES section consistent with other man pages' (e.g. exit(3) and
abort(3)

Patch provided by Bug Hunting.

branches: 1.20.2;
add vpanic

Assign copyright to TNF

mention panic uses.

branches: 1.17.28; 1.17.32;
Bump date for previous.

another documentation update for ddb.onpanic. this time, rewrite it to
refer to options(4) rather than add a new description of what its values
can be.

Use
.In header.h
instead of
.Fd #include \*[Lt]header.h\*[Gt]
Much easier to read and write, and supported by groff for ages.
Okayed by ross.

Add a line saying that a trailing '\n' is not needed. Bump date.
While here: new sentence, new line.

Fix .Fn arguments.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

Sort SEE ALSO.

the dump device isn't hardcoded into compiled kernel commonly nowadays
xref swapctl(8)

Boring whitespace fixes.

If db_onpanic is unset and DDB is compiled in, panic() now calls
db_stack_trace_print(__builtin_frame_address(0),...), to printf() the
stack trace to the message bufffer and console. Idea from SunOS/Solaris.
Useful when dumping fails.

Fix formatting errors (bad sentence breaks).

Eliminate extra comma in SEE ALSO section

Cleaned up some statements.
Added cross references to related pages.

macroize BSD, NetBSD, FreeBSD and misc cleanup

Typo.

add copyright and netbsd rcs tag

add panic(9) man page