Added the length argument to a std::string argument, under Linux it

compiled with the default value npos, under Windows it broke the build,
add the npost excpilicity should get round this difference in implementation.

src/osgDB/Registry.cpp

@@ -1184,7 +1184,7 @@ void Registry::convertStringPathIntoFilePathList(const std::string& paths,FilePa
             start = end+1;
         }
 
-        filepath.push_back(std::string(paths,start));
+        filepath.push_back(std::string(paths,start,std::string::npos));
     }
  
 }