fix build failures with newer compiler versions

src/Mod/Image/Gui/CMakeLists.txt

@@ -14,6 +14,12 @@ include_directories(
     ${XercesC_INCLUDE_DIRS}
 )
 
+if(MSVC)
+    include_directories(
+        ${CMAKE_SOURCE_DIR}/src/3rdParty/OpenGL/api
+    )
+endif(MSVC)
+
 set(ImageGui_LIBS
     Image
     FreeCADGui

src/Mod/Image/Gui/OpenGLImageBox.cpp

@@ -39,9 +39,13 @@
 # include <Windows.h>
 # include <GL/gl.h>
 # include <GL/glu.h>
+# if defined(_MSC_VER) && _MSC_VER >= 1910
+# include <GL/glext.h>
+# endif
 #else
 # include <GL/gl.h>
 # include <GL/glu.h>
+# include <GL/glext.h>
 #endif
 
 #include "OpenGLImageBox.h"