Added missing include

src/slic3r/GUI/OpenGLManager.cpp

@@ -12,6 +12,7 @@
 #include <boost/log/trivial.hpp>
 
 #include <wx/glcanvas.h>
+#include <wx/msgdlg.h>
 
 #if ENABLE_HACK_CLOSING_ON_OSX_10_9_5
 #ifdef __APPLE__

src/slic3r/GUI/OpenGLManager.hpp

@@ -1,6 +1,7 @@
 #ifndef slic3r_OpenGLManager_hpp_
 #define slic3r_OpenGLManager_hpp_
 
+class wxWindow;
 class wxGLCanvas;
 class wxGLContext;