Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Import NetBSD readline.c,v 1.104: do not crash with add_history(NULL).

MFC after: 3 days
Approved by: re (gjb)

* Add the readline(3) API to libedit. The libedit versions of
{readline,history}.h are in /usr/include/edit so as to not conflict with
the GNU libreadline versions. To use the libedit readline(3) one should
add "-I/usr/include/edit" to their Makefile
(spelled "-I${DESTDIR}/${INCLUDEDIR}/edit" within the FreeBSD source tree).

* Enable its use in the BSD licensed utilities that support readline(3).

* To make it easier to sync libedit development with NetBSD, histedit.h
is moved into libedit's directory as history shows shown we keep merging
it into that location.

Obtained from: NetBSD
Sponsored by: Juniper Networks

Vendor import NetBSD's libedit of "2010/08/04 20:29:18 UTC".

Obtained from: NetBSD

Vendor import NetBSD's libedit of "2010/06/01 18:20:26 UTC".

Obtained from: NetBSD

Vendor import NetBSD's libedit of "2007/01/12 16:31:13 UTC".

Obtained from: NetBSD

Vendor import NetBSD's libedit of "2006/03/23 20:22:51 UTC".

Obtained from: NetBSD

Vendor import NetBSD's libedit of "2005/08/02 12:11:14 UTC".

Obtained from: NetBSD

Vendor import NetBSD's libedit of "2001/09/29 17:52:10 UTC".

Obtained from: NetBSD