From Eric Sokolowsky, warning fixes for g++ 4.0 under Fedora Core 4.

include/osg/Array

@@ -286,6 +286,7 @@ class ArrayVisitor
 {
     public:
         ArrayVisitor() {}
+        virtual ~ArrayVisitor() {}
         
         virtual void apply(Array&) {}
         virtual void apply(ByteArray&) {}
@@ -315,6 +316,7 @@ class ConstArrayVisitor
 {
     public:
         ConstArrayVisitor() {}
+        virtual ~ConstArrayVisitor() {}
         
         virtual void apply(const Array&) {}
         virtual void apply(const ByteArray&) {}
@@ -345,6 +347,7 @@ class ValueVisitor
 {
     public:
         ValueVisitor() {}
+        virtual ~ValueVisitor() {}
         
         virtual void apply(GLbyte&) {}
         virtual void apply(GLshort&) {}
@@ -374,6 +377,7 @@ class ConstValueVisitor
 {
     public:
         ConstValueVisitor() {}
+        virtual ~ConstValueVisitor() {}
         
         virtual void apply(const GLbyte&) {}
         virtual void apply(const GLshort&) {}

include/osg/Shape

@@ -104,6 +104,7 @@ class ShapeVisitor
     public:
     
     	ShapeVisitor() {}
+        virtual ~ShapeVisitor() {}
     
     	virtual void apply(Sphere&) {}
     	virtual void apply(Box&) {}
@@ -124,6 +125,7 @@ class ConstShapeVisitor
     public:
     
     	ConstShapeVisitor() {}
+        virtual ~ConstShapeVisitor() {}
 
     	virtual void apply(const Sphere&) {}
     	virtual void apply(const Box&) {}

include/osg/StateAttribute

@@ -258,6 +258,7 @@ class OSG_EXPORT StateAttribute : public Object
 
         struct ModeUsage
         {
+            virtual ~ModeUsage() {}
             virtual void usesMode(GLMode mode) = 0;
             virtual void usesTextureMode(GLMode mode) = 0;
         };