msmtp: 1.4.30 -> 1.4.31

Also, set meta.platforms and fix meta.description (msmtp is not a MUA).

pkgs/applications/networking/msmtp/default.nix

@@ -1,18 +1,20 @@
 { stdenv, fetchurl, openssl, pkgconfig, gnutls, gsasl, libidn }:
+
 stdenv.mkDerivation rec {
-  name = "msmtp-1.4.30";
+  name = "msmtp-1.4.31";
 
   src = fetchurl {
     url = "mirror://sourceforge/msmtp/${name}.tar.bz2";
-    sha256 = "11lq82byx9xyfkf4nrcfjjfv5k8gk3bf8zlw0kml1qrndqlvjlpi";
+    sha256 = "0pr29kb7qsz4q6yfw5wvmw1wm4axi8kc97qhhmp50bx2bylzjyi4";
   };
 
   buildInputs = [ openssl pkgconfig gnutls gsasl libidn ];
 
   meta = {
-      description = "a MUA";
+      description = "Simple and easy to use SMTP client with excellent sendmail compatibility";
       homepage = "http://msmtp.sourceforge.net/";
       license = stdenv.lib.licenses.gpl3;
       maintainers = [ stdenv.lib.maintainers.garbas ];
+      platforms = stdenv.lib.platforms.linux;
     };
 }