MFC: r220370, r209136, r209219

MFC: r220370, r209136, r209219

* 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).
* histedit.h is moved into libedit's directory

* Add basic filename completion code.
* Allow simple quoting in filename completion.

git-svn-id: svn://svn.freebsd.org/base/stable/8@220612 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f