the global locale was generating bad dot files. Specifically, the node
numbers had comma separators in them (like 1,234 rather than 1234).
The attached file simply forces the stringstreams used to build up the
dot file to use the "C" locale."
and so, if the .dot plugin was loaded, it would happily handle any file
name extension.
To reproduce the bug, first save a scene to a dot file (to load the dot
plugin), then try to write the scene to an osg file. If you look at the
osg file, you will see that it is a dot file."
