[EMF] Protecting print of names to ensure a length < 50. Remove the middle part of the string and inject a hash of it.

[HORN] Protect names of stateless nodes with a _fun suffix. This was conflicting with existing names in Z3, ie. "abs".
[HORN] Better treatment of stateless nodes collecting semantics
       Fixes issue #13 on github: https://github.com/coco-team/lustrec/issues/13

Renamed ISet of Machine_code to VSet: was sets of variable and was conflicting with ISet from Utils which carries strings.

This is used in EMF backend.