MSC: allow to express simultaneous arrival of a message
(from redmine: issue id 1931, created on 2014-02-13, closed on 2015-01-12)
- Relations:
- relates #1932 (closed)
- relates #1930 (closed)
(from redmine: issue id 1931, created on 2014-02-13, closed on 2015-01-12)