jack: change package and attr names to 'jack1' and 'jack2'

Currently, we have a 'jack' package with attrname 'jack1d' and a
'jackdbus' package with attrname 'jackaudio'. Make it consistent 'jack1'
and 'jack2' in both package name and attrname.

This aligns the naming with what can be found on the JACK homepage.

Q: what's the difference between jack1 and jack2?
A: http://trac.jackaudio.org/wiki/Q_differenc_jack1_jack2

pkgs/applications/audio/fluidsynth/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, alsaLib, glib, jackaudio, libsndfile, pkgconfig
+{ stdenv, fetchurl, alsaLib, glib, jack2, libsndfile, pkgconfig
 , pulseaudio }:
 
 stdenv.mkDerivation  rec {
@@ -21,7 +21,7 @@ stdenv.mkDerivation  rec {
     "-framework CoreAudio";
 
   buildInputs = [ glib libsndfile pkgconfig ]
-    ++ stdenv.lib.optionals (!stdenv.isDarwin) [ alsaLib pulseaudio jackaudio ];
+    ++ stdenv.lib.optionals (!stdenv.isDarwin) [ alsaLib pulseaudio jack2 ];
 
   meta = with stdenv.lib; {
     description = "Real-time software synthesizer based on the SoundFont 2 specifications";