xautoclick: add license

pkgs/applications/misc/xautoclick/default.nix

···
     addToSearchPath PATH .bin
   '';
 
-  meta = {
-    platforms = stdenv.lib.platforms.linux;
+  meta = with stdenv.lib; {
+    description = "Autoclicker application, which enables you to automatically click the left mousebutton";
+    homepage = http://xautoclick.sourceforge.net;
+    license = licenses.gpl2;
+    platforms = platforms.linux;
   };
 }