Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

In libexec/getty/chat.c, replace && with & in chat_send(). The intent
is to test if the CHATDEBUG_SEND bit is set in the chat_debug global.

MFC after: 1 week

Add __unused. Ansi prototypes.

Include gettytab.h before extern.h so that the declarations of struct
gettyflags, gettynums and gettystrs are available.

Fixed a misspelling of 0 as NULL.

Fix typos, mostly s/ an / a / where appropriate and a few s/an/and/
Add FreeBSD Id tag where missing.

Removed unused include of <sys/resource.h> instead of depending on
namespace pollution only 1 layer deep in <sys/stat.h> for its
prerequisite <sys/time.h>

Removed other unused includes.

o __P removal
o remove register
o use strict prototypes

$Id$ -> $FreeBSD$

Correct incompletes .Xrs. Remove duplicate #includes and unused variables.

Use cgetustr() since we handled special escapes ourselves.
Fix typo in escape parsing function.
PR: 4370
Submitted by: sumii@is.s.u-tokyo.ac.jp

Revert $FreeBSD$ to $Id$

Tidy-up modem-chat handling: ensure tty modes are restored to
'sane' standard (not raw) settings before abort/exiting; move
responsibility of setting raw mode for chat-handling out of
chat.c to avoid doing redundant tc{s,g}etattr()s; move DE
pause prior setting standard mode before issue/login prompt to
avoid echoing modem connect strings. Fixed up comment styles
in a couple of places.

Added:
ic=expect/send script modem init script
ac=expect/send script modem answer script
ct#val chat script timeout (seconds)
rt#val recycle timeout (seconds) if 'ac' set
dc#val debug bitmask for debugging chat scripts
hw (boolean) enable crtscts handshaking
if=path 'issue' file sent prior login prompt

chat.c is a simplistic expect/send chat module.