Switch to side-by-side view

--- a/src/qtgui/preview_w.cpp
+++ b/src/qtgui/preview_w.cpp
@@ -14,10 +14,6 @@
  *   Free Software Foundation, Inc.,
  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  */
-#include <unistd.h>
-#include <stdlib.h>
-#include <time.h>
-#include <sys/stat.h>
 
 #include <list>
 #include <utility>