Introduced CMake option OSG_PROVIDE_READFILE option that defaults to ON, but when switched to OFF disables the building of the osgDB::read*File() methods,

forcing users to use osgDB::readRef*File() methods.  The later is preferable as it closes a potential threading bug when using paging databases in conjunction
with the osgDB::Registry Object Cache.  This threading bug occurs when one thread gets an object from the Cache via an osgDB::read*File() call where only
a pointer to the object is passed back, so taking a reference to the object is delayed till it gets reassigned to a ref_ptr<>, but at the same time another
thread calls a flush of the Object Cache deleting this object as it's referenceCount is now zero.  Using osgDB::readREf*File() makes sure the a ref_ptr<> is
passed back and the referenceCount never goes to zero.

To ensure the OSG builds when OSG_PROVIDE_READFILE is to OFF the many cases of osgDB::read*File() usage had to be replaced with a ref_ptr<> osgDB::readRef*File()
usage.  The avoid this change causing lots of other client code to be rewritten to handle the use of ref_ptr<> in place of C pointer I introduced a serious of
templte methods in various class to adapt ref_ptr<> to the underly C pointer to be passed to old OSG API's, example of this is found in include/osg/Group:

    bool addChild(Node* child); // old method which can only be used with a Node*

    tempalte<class T> bool addChild(const osg::ref_ptr<T>& child) { return addChild(child.get()); } // adapter template method

These changes together cover 149 modified files, so it's a large submission. This extent of changes are warrent to make use of the Object Cache
and multi-threaded loaded more robust.



git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@15164 16af8721-9629-0410-8352-f15c8da7e697

include/osg/Group

@@ -50,6 +50,8 @@ class OSG_EXPORT Group : public Node
         */
         virtual bool addChild( Node *child );
 
+        template<class T> bool addChild( const ref_ptr<T>& child ) { return addChild(child.get()); }
+
         /** Insert Node to Group at specific location.
           * The new child node is inserted into the child list
           * before the node at the specified index. No nodes
@@ -57,6 +59,8 @@ class OSG_EXPORT Group : public Node
         */
         virtual bool insertChild( unsigned int index, Node *child );
 
+        template<class T> bool insertChild( unsigned int index, const ref_ptr<T>& child ) { return insertChild(index, child.get()); }
+
         /** Remove Node from Group.
           * If Node is contained in Group then remove it from the child
           * list, decrement its reference count, and dirty the
@@ -67,6 +71,8 @@ class OSG_EXPORT Group : public Node
         */
         virtual bool removeChild( Node *child );
 
+        template<class T> bool removeChild( const ref_ptr<T>& child ) { return removeChild(child.get()); }
+
         /** Remove Node from Group.
           * If Node is contained in Group then remove it from the child
           * list, decrement its reference count, and dirty the
@@ -91,6 +97,8 @@ class OSG_EXPORT Group : public Node
           */
         virtual bool replaceChild( Node *origChild, Node* newChild );
 
+        template<class T, class R> bool replaceChild( const ref_ptr<T>& origChild, const ref_ptr<R>& newChild ) { return replaceChild( origChild.get(), newChild.get()); }
+
         /** Return the number of children nodes. */
         virtual unsigned int getNumChildren() const;
 
@@ -124,6 +132,8 @@ class OSG_EXPORT Group : public Node
             return false;
         }
 
+        template<class T> bool conatainsNode(const ref_ptr<T>& node) const { return containsNode(node.get()); }
+
         /** Get the index number of child, return a value between
           * 0 and _children.size()-1 if found, if not found then
           * return _children.size().