Add libwebsockets package

pkgs/development/libraries/libwebsockets/default.nix

···
+{ fetchgit, stdenv, cmake, openssl, zlib }:
+
+stdenv.mkDerivation rec {
+  name = "libwebsockets-1.4";
+
+  src = fetchgit {
+    url = "git://git.libwebsockets.org/libwebsockets";
+    rev = "16fb0132cec0fcced29bce6d86eaf94a9beb9785";
+    sha256 = "fa4c81f86dfc39211b78c53c804efc19e15b81ccb05e72699220bbed27204c7d";
+  };
+
+  buildInputs = [ cmake openssl zlib ];
+
+  meta = {
+    description = "Light, portable C library for websockets";
+    longDescription = ''
+      Libwebsockets is a lightweight pure C library built to
+      use minimal CPU and memory resources, and provide fast
+      throughput in both directions.
+    '';
+    homepage = https://libwebsockets.org/trac/libwebsockets;
+    # See http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/tree/LICENSE
+    license = stdenv.lib.licenses.gpl2Plus;
+    maintainers = [ ];
+    platforms = stdenv.lib.platforms.all;
+  };
+}

pkgs/top-level/all-packages.nix

···
 
   librdmacm = callPackage ../development/libraries/librdmacm { };
 
+  libwebsockets = callPackage ../development/libraries/libwebsockets { };
+
   limesurvey = callPackage ../servers/limesurvey { };
 
   logcheck = callPackage ../tools/system/logcheck {