Merge pull request #268 from kwatts/render_callback_virtual_dtor

Thanks for the help! Adding virtual destructor for RenderCallbacks struct

btgui/OpenGLWindow/fontstash.h

@@ -101,6 +101,7 @@ struct sth_texture
 
 struct	RenderCallbacks
 {
+	virtual ~RenderCallbacks() {}
 	virtual void updateTexture(sth_texture* texture, sth_glyph* glyph, int textureWidth, int textureHeight)=0;
 	virtual void render(sth_texture* texture)=0;
 };

src/BulletSoftBody/btSoftBody.h

@@ -171,6 +171,7 @@ public:
 	/* ImplicitFn	*/ 
 	struct	ImplicitFn
 	{
+		virtual ~ImplicitFn() {}
 		virtual btScalar	Eval(const btVector3& x)=0;
 	};
 
@@ -528,6 +529,7 @@ public:
 	{
 		struct IControl
 		{
+			virtual ~IControl() {}
 			virtual void			Prepare(AJoint*)				{}
 			virtual btScalar		Speed(AJoint*,btScalar current) { return(current); }
 			static IControl*		Default()						{ static IControl def;return(&def); }