added ability to reference clocks and specify simple quasi-synchrony
to the AGREE grammar.  You can use the statment "synchrony : n;"
in the annex of an implementation to specify that all the subcomponents
of the implementation should tick no more than n times since any other
component has ticked.  If no value for the synchrony is specified
(or if synchrony is set to zero) then the subcomponents of the
implementation behave synchronously.