From Bryan Thrall, "The .osg plugin doesn't seem to support an option to write shader files

separately, so it always inlines them in the .osg file (as far as I can
tell). This change adds that ability. "

Merged from svn/trunk.

src/osgPlugins/osg/ReaderWriterOSG.cpp

@@ -264,6 +264,10 @@ class OSGReaderWriter : public ReaderWriter
                     {
                         fout.setOutputTextureFiles(true);
                     }
+                    if (opt=="OutputShaderFiles")
+                    {
+                        fout.setOutputShaderFiles(true);
+                    }
                 }
             }
         }