cvsps: get source from Debian, fix build

The cobite.com urls seem to have disappeared or been moved.  I've failed
to find where they might have gone, so use debian's mirrored sources
instead.

pkgs/applications/version-management/cvsps/default.nix

@@ -1,9 +1,10 @@
 { fetchurl, stdenv, cvs, zlib }:
 
 stdenv.mkDerivation rec {
-  name = "cvsps-2.1";
+  name = "cvsps-${version}";
+  version = "2.1";
   src = fetchurl {
-    url = "http://www.cobite.com/cvsps/${name}.tar.gz";
+    url = "mirror://debian/pool/main/c/cvsps/cvsps_${version}.orig.tar.gz";
     sha256 = "0nh7q7zcmagx0i63h6fqqkkq9i55k77myvb8h6jn2f266f5iklwi";
   };
 
@@ -17,6 +18,7 @@ stdenv.mkDerivation rec {
   installPhase = "make install prefix=$out";
 
   meta = {
+    description = ''A tool to generate CVS patch set information'';
     longDescription = ''
       CVSps is a program for generating `patchset' information from a
       CVS repository.  A patchset in this case is defined as a set of
@@ -25,5 +27,6 @@ stdenv.mkDerivation rec {
     '';
     homepage = http://www.cobite.com/cvsps/;
     license = stdenv.lib.licenses.gpl2;
+    platforms = stdenv.lib.platforms.unix;
   };
 }