Add zlib license.

debian/copyright

@@ -90,7 +90,7 @@ License: MIT-like
 Files: Utilities/cmzlib/*
 Copyright: 1995-2005 Jean-loup Gailly
   1995-2005 Mark Adler
-License: zlib/libpng FIXME
+License: zlib
 
 License: BSD-3-clause
  Copyright (c) 2002 Kitware, Inc., Insight Consortium
@@ -413,3 +413,20 @@ License: BSD-2-clause
   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE.
+
+License: zlib
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+  .
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+  .
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.