lstat: fix Solaris 9 bug

lstat: fix Solaris 9 bug

lstat("file/",buf) mistakenly succeeded.

* lib/lstat.c (lstat): Also check for trailing slash on
non-symlink, non-directories.  Use stat module to simplify logic.
* doc/posix-functions/lstat.texi (lstat): Document it.
* modules/lstat-tests (Depends-on): Add errno, same-inode.
(configure.ac): Check for symlink.
* tests/test-lstat.c (main): Add more tests.

Signed-off-by: Eric Blake <ebb9@byu.net>