openjdk10: gtk2 -> gtk3

http://openjdk.java.net/jeps/283 "Enable GTK 3 on Linux" was included
in OpenJDK 9.

nothing else currently in nixpkgs is using 10, so this just lets us
establish a good baseline as things are ported onto it.  if needed,
the build could be parameterized so that any packages that turn out to
need gtk2 could still use it.

pkgs/development/compilers/openjdk/10.nix

@@ -4,7 +4,7 @@
 , libjpeg, giflib
 , setJavaClassPath
 , minimal ? false
-, enableGnome2 ? true, gtk2, gnome_vfs, glib, GConf
+, enableGnome2 ? true, gtk3, gnome_vfs, glib, GConf
 }:
 
 let
@@ -38,7 +38,7 @@ let
       libjpeg giflib libX11 libICE libXext libXrender libXtst libXt libXtst
       libXi libXinerama libXcursor lndir fontconfig
     ] ++ lib.optionals (!minimal && enableGnome2) [
-      gtk2 gnome_vfs GConf glib
+      gtk3 gnome_vfs GConf glib
     ];
 
     patches = [
@@ -80,7 +80,7 @@ let
     NIX_LDFLAGS= lib.optionals (!minimal) [
       "-lfontconfig" "-lcups" "-lXinerama" "-lXrandr" "-lmagic"
     ] ++ lib.optionals (!minimal && enableGnome2) [
-      "-lgtk-x11-2.0" "-lgio-2.0" "-lgnomevfs-2" "-lgconf-2"
+      "-lgtk-3" "-lgio-2.0" "-lgnomevfs-2" "-lgconf-2"
     ];
 
     buildFlags = [ "all" ];