MFC r359680: mail/gprof/tip: tap with the ugly stick

The ugly stick here is this bit in the respective headers:

#ifndef EXTERN
#define EXTERN extern
#endif

with a follow-up #define EXTERN in a single .c file to push all of their
definitions into one spot. A pass should be made over these three later to
push these definitions into the correct files instead, but this will suffice
for now and at a more leisurely pace.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Spelling fixes for usr.bin/

Fix typos - remove duplicate "is".

PR: docs/154934
Submitted by: Eitan Adler <lists at eitanadler.com>
MFC after: 3 days

Relinquish exclusive TTY access when tip(1) or cu(1) exit.
Previously they would have left TIOCEXCL enabled, requiring
either a reboot or use of tip/cu as the root user.

Observed when running QEMU with character devices redirected to pty instances.

MFC after: 2 weeks

Resolve merge conflicts.

Use a proper protoype to declare interp() and move it to tip.h. Fix an
invocation with a wrong number of arguments.

Approved by: das (mentor)

make prototpyes match functions, and declare things static as needed

remove __P

Fix merge conflicts, and because this still has a zillion warnings,
protect the build with a WARNS=2.

Fix the build.

#include <errno.h> where needed. Kill extern int errno;.

Minor warnings in tip corrected.

Rename a function to avoid conflict with the new syscall 'pwrite'.

Change from using sys/param.h and MAXPATHLEN to using limits.h and PATH_MAX
to avoid the NOFILE problem. Back out NOFILE kludge. Fix unexploitable
buffer overflow in tipout.c.
Reviewed by: millert@openbsd.org (tipout.c)
Submitted by: millert@openbsd.org (rest of idea)

Fix buffer overflow. prompt didn't get a size for its buffer,
so it could overflow it. Also made some filenames MAXPATHLEN long rather
than 80 long.

Add prototypes, usage(). Use err(3).

Tom Gray's new tip changes to support a modem capabilities database and
fixes to many assorted bugs and misfeatures.
Submitted by: Tom Gray - DCA <dcasba@rain.org>