Changes includes:
1. A new GifImageStream class (inherit from osg::ImageStream and OpenThreads::Thread) have already been added to implement different operations of a GIF movie, such like playing, pausing, rewinding, setting time and so on.
2. Some small changes to decode_row() and gif_read_stream(), which make the transparency of GIF images correctly.
3. Just a few changes to the ReaderWriterGIF::readGIFStream() function, which ensure that animate GIFs are loaded by GifImageStream (and the function returns GifImageStream objects) and static GIFs unchanged (still use the old method and returns osg::Image objects!).
Attachments are the cpp file and an animate GIF file for further test. Just rebuild the osgdb_gif project and use osgviewer or osgmovie to view it.
The plugin has been tested on Windows and Arch Linux."