wxWidgets 2.8 compatibility fix.

common/drawpanel_gal.cpp

@@ -53,7 +53,8 @@ EDA_DRAW_PANEL_GAL::EDA_DRAW_PANEL_GAL( wxWindow* aParentWindow, wxWindowID aWin
 
     wxStandardPaths paths;
     wxFileName executableFile( paths.GetExecutablePath() );
-    m_galShaderPath = std::string( executableFile.GetPath() + "/../../common/gal/opengl/shader/" );
+    m_galShaderPath = std::string( ( executableFile.GetPath() +
+                                   wxT( "/../../common/gal/opengl/shader/" ) ).mb_str() );
 
     SwitchBackend( aGalType, false );
     SetBackgroundStyle( wxBG_STYLE_CUSTOM );