[libedit] sync with NetBSD

[bapt]

Summary

Upstream (NetBSD) has been fixed many bugs in libedit.
To reduce the difference from upstream,
we import libedit again.

According to NetBSD commit log, following bugs have been fixed.

• NetBSD bug database

PR/54415
PR/54399
PR/54400
PR/54329
PR/54281
PR/54280
PR/54279
PR/54131
PR/52359
PR/54117
PR/54067
PR/53983
PR/53981
PR/53856
PR/53803

Major souce code style changes:

• omit WIDECHAR definition. It became default.
• changed wide charactor type from 'Char' to 'wchar_t'.
• changed 'private' keyword to 'static'.
• changed 'protected' keyword to 'libedit_private'.
• 'public' keyword has been omitted.

New manual page:

• editline.7 has been added.

Function changes:

• _el_fn_sh_complete() has been deleted.
• completion_matches() has changed its parameter.
• rl_reset_terminal() has changed return type.
• rl_stuff_char() has changed return type.

So we need to bump up library version from 7 to 8.

[bcr]

OK from manpages.

[naito.yuichiro_gmail.com]

re-sync with NetBSD on Wed Aug 21 11:11:48 2019 +0000.
updated FreeBSD base revision.

[naito.yuichiro_gmail.com]

Current Status is work in progress.
I'm not sure that all bugs (that is reported in NetBSD bug database) are reproducible on FreeBSD.
I saw that OpenBSD guy said libedit had a serious problem in https://marc.info/?l=openbsd-tech&m=156463894328592&w=2.
It is my motivation for this patch.

[bapt]

Sorry I have missed this review. I already imported a newer snapshot of libedit in base. I did it through a new import due to the fact the historical import was messy (svn internal kitchen sink) see: D21584

[naito.yuichiro_gmail.com]

@bapt
Never mind. I know updating lib/libedit is a tough job.
I will see your differential D21584.

[bapt]

This has been done in rS352275