[Gnash-dev] heart-beating

[strk]

After a talk with zou about MovieAdvancement issues
[http://wiki.gnashdev.org/MovieAdvancement]
we decided to try the heart-beating way.

Basically, movie_root::advance() won't assume to be
called on SWF FPS rate anymore, but instead would check
the VirtualClock to decide wheter or not to advance the 
movie, but will take a chance to run expired timers.

Beside behavioural correctness for user-defined timers,
this will also fix a few issues on dynamically loaded
media rate, as we won't need that to be bound to SWF
frame rate anymore. Also, it opens the doors to thread-less
loading of resources since I committed a non-blocking
interface of IOChannel.

Keeping the ::advance() signature and the single entry
point drops the need to touch every gui. The only change
required will be in Player, where a default initial rate
of 10ms delay will be used.

Later we can fine-tune timers to eventually optimize
time spent on checking what's left to do.

Comments welcome.

--strk; 

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