Animated image API.

Animated image API.
http://lists.gnu.org/archive/html/emacs-devel/2010-03/msg00211.html

* image.el (image-animate-max-time): New defcustom.
(image-animated-types): New defconst.
(create-animated-image, image-animate-timer)
(image-animate-start, image-animate-stop, image-animate-timeout)
(image-animated-p): New functions.

* image-mode.el (image-toggle-display-image):
Replace `create-image' with `create-animated-image'.