Qt: Add @2x images to the layout preferences.

Run compress-pngs on the normal and @2x images.

Change-Id: Ic5bc3c42273078f32511d986b299d8606c016f6d
Reviewed-on: https://code.wireshark.org/review/7499
Reviewed-by: Gerald Combs <gerald@wireshark.org>

Makefile.am

@@ -916,11 +916,17 @@ EXTRA_DIST = \
 	image/languages/pl.svg		\
 	image/languages/zh_CN.svg	\
 	image/layout_1.png		\
+	image/layout_1@2x.png		\
 	image/layout_2.png		\
+	image/layout_2@2x.png		\
 	image/layout_3.png		\
+	image/layout_3@2x.png		\
 	image/layout_4.png		\
+	image/layout_4@2x.png		\
 	image/layout_5.png		\
+	image/layout_5@2x.png		\
 	image/layout_6.png		\
+	image/layout_6@2x.png		\
 	image/libwireshark.rc.in	\
 	image/libwsutil.rc.in		\
 	image/lo16-app-wireshark.png	\

image/layout.qrc

@@ -1,10 +1,16 @@
 <RCC>
     <qresource prefix="/layout">
         <file>layout_1.png</file>
+        <file>layout_1@2x.png</file>
         <file>layout_2.png</file>
+        <file>layout_2@2x.png</file>
         <file>layout_3.png</file>
+        <file>layout_3@2x.png</file>
         <file>layout_4.png</file>
+        <file>layout_4@2x.png</file>
         <file>layout_5.png</file>
+        <file>layout_5@2x.png</file>
         <file>layout_6.png</file>
+        <file>layout_6@2x.png</file>
     </qresource>
 </RCC>