Created a simple XmlNode parser class for reading of basic xml files, such as used by present3D.

Converted Present3D across from using libxml2 to using the new osgDB::XmlNode/XmlNode::Input classes from Xml Parsing.
This changes removes the dependency on libxml2, and allows the present3D application and p3d to work on all platforms.

src/osgDB/DynamicLibrary.cpp

@@ -139,7 +139,7 @@ DynamicLibrary::PROC_ADDRESS DynamicLibrary::getProcAddress(const std::string& p
     if (_handle==NULL) return NULL;
 #if defined(WIN32) && !defined(__CYGWIN__)
     return (DynamicLibrary::PROC_ADDRESS)GetProcAddress( (HMODULE)_handle,
-                                                         procName.c_str() );
+                                                         procName.c_str() );   /* FIX WARNING */
 #elif defined(__APPLE__) && defined(APPLE_PRE_10_3)
     std::string temp("_");
     NSSymbol symbol;