Can't create message after self message of implementation class

[Matthias Schoettle]

Given a class which extends an implementation class. If the class calls "itself" with an operation of the implementation class, no message can be created after.

See the following example, where Object.hashCode() is called:

[Matthias Schoettle]

Resolves #452: Improves the check on whether message creation is allowed after the receive event.

Separates the condition depending on the type of class. For implementation classes, it is only possible for self messages. For classes, it is possible if it is a self message, or no message view defined.

→ <<cset 7ac172af035d>>