tests: add a test to exercise today's ls-lL-vs-ACL bug

tests: add a test to exercise today's ls-lL-vs-ACL bug

* tests/ls/slink-acl: New file.
* tests/Makefile.am (TESTS): Add it.
* tests/init.cfg (require_setfacl_): New function.
* gnulib: Update to latest, for file-has-acl changes.
* NEWS (Bug fixes): Mention it.
See http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/28538.  This
":>k; setfacl -m m::r k; ln -s k s; ls -Log s" should print e.g.,
    -rw-r-----+ 1 0 Oct  5 19:22 s
With the ls from coreutils-8.13, it would print this (with "." or
nothing in place of the "+"):
    -rw-r-----. 1 0 Oct  5 19:22 s