Changed to using osgDB::ofstream to work around Windows build issue

git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14794 16af8721-9629-0410-8352-f15c8da7e697

src/osgPlugins/osgjs/json_stream

@@ -22,11 +22,12 @@
 #include <iomanip>
 #include <cctype>  // control characters
 #include <sstream>
-#include <fstream>
 #include <string>
 #include <cmath>
 #include <limits>
 
+#include <osgDB/fstream>
+
 using namespace std;
 
 // A simple class wrapping ofstream calls to enable generic cleaning of json data.
@@ -35,7 +36,7 @@ using namespace std;
 // * disallow some control characters
 // * does not support inf or nan values
 
-class json_stream : public std::ofstream {
+class json_stream : public osgDB::ofstream {
     public:
         json_stream(const std::string& filename, bool strict=true) :
             _stream(filename.c_str()),