s3:configure: require tevent >= 0.9.18 as external library

0.9.16 might be enough, but this matches the waf build.
So 0.9.18 is less likely to produce regressions in the future.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10330
Signed-off-by: Stefan Metzmacher <metze@samba.org>
s3: smbpasswd - fix crashes on invalid input.

get_pass can return NULL on error. Ensure that
this is always the case and fix all callers to cope
(some already did).

Reported by Joonas Kuorilehto <joneskoo@codenomicon.com>

BUG: https://bugzilla.samba.org/show_bug.cgi?id=10320

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Mon Dec 16 15:17:58 CET 2013 on sn-devel-104

(cherry picked from commit ef5a3bedab74420baf0c653cf8e304fe6c2a13b4)
ldb: bad if test in ldb_comparison_fold()

Found by David Binderman <dcb314@hotmail.com>

BUG: https://bugzilla.samba.org/show_bug.cgi?id=10305

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>

Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Sat Dec  7 11:10:47 CET 2013 on sn-devel-104

Autobuild-User(v4-0-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-0-test): Sat Dec 28 23:21:12 CET 2013 on sn-devel-104