GCC 4.7 fixes.

Thanks to Francois Andriot.
(cherry picked from commit 6469277159)

src/mainwindow.cpp

@@ -53,6 +53,7 @@
 #include "core/drophandler.h"
 #include "latin1literal.h"
 
+#include <unistd.h>
 #include <kapplication.h>
 #include <kcombobox.h>
 #include <kiconloader.h>