Split expressions into atomic expressions. In other words, introduce

as many  new local  variables as necessary  so that an  expression is
made at most of one operator.

The rational  for that  is to obtain  a lic  code that is  trivial to
clock check (nested node calls, for example, make it less simple).

The old behavior can still be obtained using --keep-nested-calls.

During  that  change,   I  realised  that  I  did   not  clock  check
asserts. Hence, I have also added this check.