The exception associated to each process was relocated from the

The exception associated to each process was relocated from the
context to the simix process that contains it. This is both faster and
simpler because the initialization code was factorized and exception
fetching uses one dereference less.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@6594 48e7efb5-ca39-0410-a469-dd3cf9ba447f