Initial import of advi.

Initial import of advi.

Active-DVI is a DVI previewer and presenter written in Objective Caml
(http://caml.inria.fr/ocaml/) with some eye candy effects for
presentation, support for interactive demonstrations, and embedding of
arbitrary applications within the presentation (hence the Active
adjective of the presenter :).

Active-DVI currently supports the following features:

+ Encapsulated Postscript File inclusion (using graphics package)
+ Effects for presentation (pause, delay, text color change)
+ Embedded applications for interactive demonstration
+ Pictures visualization via gpic specials
+ Display of inlined Postscript using gs
+ Font antialiasing that takes background colors into account
+ Page display is interrupted on user input
+ Resizing the page adjusts the magnification
+ Start displaying at a given page or at a given link reference
+ The file is reloading on signal SIGUSR1
+ Hyperlinks
+ Active areas (execute an action when the mouse is over)
+ Background colors and images
+ Alpha blending for images