[Gif] Restrict the memory consumption to 82944000 bytes (about 79 MB), which is equivalent to 10 full hd frames.
[Gif] Add LoadGifMetaData(...) and expose m_numFrames.
[FileItem/Picture] Add IsAnimatedPicture() to fileItem and m_isAnimated to PictureInfoTag.
[Need help] GUIWindowPictures: Play animated pictures.