539220 : GLCanvas does not work with GTK3

Specify GDK_WA_VISUAL constant depending weather GTK2 or GTK3 is used.

Use the snippet in bug description and follow the
instructions to run the snippet.

No JUnit Tests performed

Change-Id: Id8f9272f3e8248422a7c6e38e027a55425fc68b2
Signed-off-by: Felix Hirsch <felix.hirsch@gmail.com>

bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GDK.java

diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GDK.java b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GDK.java
index 2fca225..108e09d 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GDK.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/GDK.java
@@ -252,7 +252,7 @@
 	public static final int GDK_UNMAP = 15;
 	public static final int GDK_WA_X = 1 << 2;
 	public static final int GDK_WA_Y = 1 << 3;
-	public static final int GDK_WA_VISUAL = 1 << 6;
+    public static final int GDK_WA_VISUAL = GTK.GTK3 ? (1<<5) : (1<<6);
 	public static final int GDK_WINDOW_TYPE_HINT_DIALOG = 1;
 	public static final int GDK_WINDOW_TYPE_HINT_UTILITY = 5;
 	public static final int GDK_WINDOW_TYPE_HINT_TOOLTIP = 10;