### Subst: convert definitions into axioms when needed

subst can make constant definitions recursive, making them fail termination check. Convert such definitions into axioms on the fly. Tentative fix for #195.

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subst can make constant definitions recursive, making them fail termination check. Convert such definitions into axioms on the fly. Tentative fix for #195.

Showing
with
**28 additions**
and
**11 deletions**
**+28**
**-11**