httping: add optional fftw for better graphing

Enabled by default.

pkgs/tools/networking/httping/default.nix

···
-{ stdenv, fetchurl, gettext, ncurses, openssl }:
+{ stdenv, fetchurl, gettext, ncurses, openssl
+, fftw ? null }:
 
 stdenv.mkDerivation rec {
   name = "httping-${version}";
···
     sha256 = "1110r3gpsj9xmybdw7w4zkhj3zmn5mnv2nq0ijbvrywbn019zdfs";
   };
 
-  buildInputs = [ ncurses openssl ];
+  buildInputs = [ fftw ncurses openssl ];
   nativeBuildInputs = [ gettext ];
 
   makeFlags = [
···
     inherit version;
     homepage = http://www.vanheusden.com/httping;
     description = "ping with HTTP requests";
+    longDescription = ''
+      Give httping an url, and it'll show you how long it takes to connect,
+      send a request and retrieve the reply (only the headers). Be aware that
+      the transmission across the network also takes time! So it measures the
+      latency of the webserver + network. It supports IPv6.
+    '';
     maintainers = with maintainers; [ nckx rickynils ];
-    platforms = with platforms; linux;
+    platforms = platforms.linux;
   };
 }