pass lint.

Remove unused stuff, and limit the scope of some of the used ones.
(from des@freebsd)

s/protected/libedit_private/g

Instead of compiling all the source files together in one big file, use
protected visibility to achieve the same effect.

Get rid of private/public; keep protected (Ingo Schwarze)

Start removing the WIDECHAR ifdefs; building without it has stopped working
anyway. (Ingo Schwarze)

whitespace and header sorting changes (Ingo Schwarze). No functional changes.

- don't set _GNU_SOURCE. We are not supposed to make decisions for others.
- don't special-case wcsdup()
From Ingo Schwarze.

OpenBSD readline.c rev. 1.14 2015/02/06 23:21:58 millert
use SIZE_MAX

forgot one fgetln define

change tests for fgetln.

- Add some more Char casts
- reduce ifdefs by providing empty defs for nls functions (Ingo Schwarze)

include <wchar.h> if we don't have wcsdup()

kill ifdef notdef

kill ptr_t and ioctl_t, add * sizeof(*foo) to all allocations.

more portability defines

Wide character support (UTF-8) from Johny Mattsson; currently disabled.

delete defined(sun), it could be invaded in the user namespace. Suggested
by mrg@

use __sun || sun instead of _SunOS, from Jess Thrysoee

SUNOS is spelt __SunOS. Add missing prototypes.

portability fixes.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22280, verified by myself.

provide a definition for __attribute__

- include cdefs.h early in the game
- ifdef notdef the sunos stuff
- no need for sig_t

- constify; passes all gcc and lint strict checks.
- add config.h [Jason Evans], to create a portable version of libedit that
can be easily compiled on other OS's.