Bugfix : nested for loop doesn't catch assignation effect correctly

type:fixed

Bug reported in #1449 (closed)

The purification algorithm didn't propagate correctly effect detected in a fonction to the call of this function.(i.e. Effect pass in recursion style instead of fold style).

This is a quickfix to this issues. We may want to rewrite the detection algorithm to have a proper fold style.

Changelog details: Fixing bug with nested for loops in Pascaligo