PSSM_ — "Join 003" has (invalid) triggers on transitions entering join

According to the UML 2.5.1 spec, there's a constraint `join_segment_guards` which prohibits transitions whose target is a join pseudostate from having guards or triggers (the constraint's scope is larger than its name would imply). But the sample state machine "Join 003" has triggers on the two transitions entering the join.

Essentially, as I read the UML spec, transitions leading to joins can only be triggered by completion events.

I don't think that restriction is necessary, and can be trivially worked around (make a composite state with a triggered transition entering the final state). But this state machine does appear to violate that constraint.

Merge with PSSM_-8

This issue relates to the same element of the same test case, Join 003, as issue PSSM_-8. The two issues can therefore be resolved together.