added zlib copyright and fixed libgit copyright format

debian/copyright

@@ -4,7 +4,7 @@ Source: http://libgit2.github.com/
 
 Files: *
 Copyright: Copyright (C) 2009-2011 the libgit2 contributors
-License: GPLv2 with a special Linking Exception
+License: GPL-2 with a special Linking Exception
  libgit2 is Copyright (C) 2009-2011 the libgit2 contributors,
  unless otherwise stated. See the AUTHORS file for details.
  .
@@ -91,7 +91,30 @@ License: MIT
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  IN THE SOFTWARE. 
+
  
+Files: deps/zlib/*
+Copyright: Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
+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.
+ .
+ Jean-loup Gailly        Mark Adler
+ jloup@gzip.org          madler@alumni.caltech.edu
+
 
 Files: debian/*
 Copyright: 2011 Russell Sim <russell.sim@gmail.com>