Start the implementation of start_time and kill_time in the msg deployment.

First bad news, I had to change the prototype of
MSG_process_create_with_arguments. But until we use an option set here,
there is no way to let the code evolving without such breakage (TODO).

Second bad news: I didn't manage to implement start_time, ie to let
processes sleep an arbitrary amount of time even before running at the first
place.

Third bad news: kill_time implementation seems buggy: examples/gras/ping
hangs when the client has kill_time=0.8, ie when it dies during its sleep. I
suspect a bug somewhere in MSG_process_kill

In summary, Arnaud, please heeeelp :-/

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@1296 48e7efb5-ca39-0410-a469-dd3cf9ba447f