[osg-submissions] 8581 is broken

[James Killian]

I've found and fixed my build I think there are some merging errors... here 
is what I did.

applications/osgconv/osgconv.cpp line 58
//supportedExtension() drop the s
            rwi->extensions = rw->supportedExtension();

include/osgDB/Registry
    //moved this to public since osgconv needs it
 typedef std::vector< osg::ref_ptr<ReaderWriter> > 
ReaderWriterList;
    //added this since osgconv needs it
const Registry::ReaderWriterList &getReaderWriterList() {return _rwList;}

I am not sure if this is correct so could someone please check these files 
out, and fix.  Thanks.