Bug 374985 - [GTK/Linux] red background of min/max icons on gtk64

SWT fails to find the transparent color in the palette of the image data
created by GTK if the palette is reduced to 16 bit (e.g. in a vnc session
with 16 bit color depth).

The solution is: just use slightly different color value for the transparent
pixel which fits into 16 bit color palette and can be found later by
imageData.palette.getPixel(transparent).

See proposal made in bug 374985 comment 9 by Daniel Friederich.

Change-Id: I216227be1e5fa2a16ce12cb36c7c84951394e29e
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Also-by: Daniel Friederich <danielfriederich@gmx.net>
diff --git a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java
index db36c85..c2e9be3 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java
@@ -737,7 +737,7 @@
 	if (button == CTabFolderRenderer.PART_CHEVRON_BUTTON) {
 		transparent = new RGB(0xFF, 0xFF, 0xFF);
 	} else {
-		transparent = new RGB(0xFD, 0, 0);
+		transparent = new RGB(0xF7, 0, 0);
 	}
 	Color transColor = new Color(display, transparent);
 	gc.setBackground(transColor);