Oops. Put an important #include back

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402363

dlib/gui_core/gui_core_kernel_2.cpp

@@ -24,6 +24,7 @@
 #include "../logger.h"
 #include <vector>
 #include <set>
+#include "../gui_widgets/fonts.h"
 
 namespace dlib
 {