Revision 671168

Changed return type for FirstOrderIntegrator.integrate() to double
in order to retrieve exact stop time. This allows to handle properly
integration interruption due to an EventHandler instance asking to
stop the integration when its associated event is triggered. The state
was already set to the current state at interruption time, but it was
difficult to get the corresponding time (it involved setting a step
handler monitoring the last step specially).

JIRA: MATH-213