hg: openjfx/jfx-dev/rt: 8198654: Switch FX's default GTK version to 3

[kevin.rushforth at oracle.com]

Changeset: 3e6c9b6db694
Author:    kcr
Date:      2018-03-20 13:01 -0700
URL:       http://hg.openjdk.java.net/openjfx/jfx-dev/rt/rev/3e6c9b6db694

8198654: Switch FX's default GTK version to 3
Reviewed-by: prr

! modules/javafx.graphics/src/main/java/com/sun/glass/ui/gtk/GtkApplication.java
! modules/javafx.graphics/src/main/native-glass/gtk/launcher.c