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/misc/emulators/mednafen/default.nix

@@ -1,6 +1,6 @@
 { stdenv, fetchurl, pkgconfig
 , libX11, mesa, freeglut
-, jackaudio, libcdio, libsndfile, libsamplerate
+, jack2, libcdio, libsndfile, libsamplerate
 , SDL, SDL_net, zlib
 }:
 
@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
   };
 
   buildInputs = with stdenv.lib;
-  [ libX11 mesa freeglut jackaudio libcdio libsndfile libsamplerate SDL SDL_net zlib ];
+  [ libX11 mesa freeglut jack2 libcdio libsndfile libsamplerate SDL SDL_net zlib ];
   
   nativeBuildInputs = [ pkgconfig ];