re-add symbol export

When compiling with hidden visiblity, using operator<< on a VrmlNode
from outside the vrml library proper requires that this operator is
exported. So re-add the export, but this time before the friend
declaration, assuming that the compile problems on windows stem from the
fact that the first declaration (as a friend) did not specify all
decorators.

Author: aumuell

src/OpenCOVER/vrml97/vrml/VrmlNode.h

@@ -51,8 +51,11 @@ namespace vrml{
 
 class VrmlScene;
 class Viewer;
-
+class VrmlNode;
 class VrmlNodeUpdateRegistry;
+
+std::ostream &VRMLEXPORT operator<<(std::ostream &os, const VrmlNode &f);
+
 class VRMLEXPORT VrmlNode
 {
     friend class VrmlNodeUpdateRegistry;
@@ -354,8 +357,6 @@ class VRMLEXPORT VrmlNode
 
 };
 
-std::ostream &operator<<(std::ostream &os, const VrmlNode &f);
-
 template<typename VrmlType>
 VrmlField::VrmlFieldType toEnumType(const VrmlType *t = nullptr);