Install viewer .desktop file and icons on all Unix systems

These files are not Red Hat or Ubuntu specific, so install them
on all Unix systems where the viewer is installed.
diff --git a/vncviewer/CMakeLists.txt b/vncviewer/CMakeLists.txt
index de9da8f..f2a0aca 100644
--- a/vncviewer/CMakeLists.txt
+++ b/vncviewer/CMakeLists.txt
@@ -55,4 +55,10 @@
 install(TARGETS vncviewer DESTINATION ${BIN_DIR})
 if(UNIX)
   install(FILES vncviewer.man DESTINATION ${MAN_DIR}/man1 RENAME vncviewer.1)
+  configure_file(vncviewer.desktop.in vncviewer.desktop)
+  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/vncviewer.desktop DESTINATION ${DATA_DIR}/applications)
+  foreach(res 16 22 24 32 48)
+    install(FILES ../media/icons/tigervnc_${res}.png DESTINATION ${DATA_DIR}/icons/hicolor/${res}x${res}/apps RENAME tigervnc.png)
+  endforeach()
+  install(FILES ../media/icons/tigervnc.svg DESTINATION ${DATA_DIR}/icons/hicolor/scalable/apps)
 endif()