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     The order of the `exec` is the priority order for being the
shortcut. cvc4 should point to the latest or cvc4 if present

- make Whyconf.Args.initialize return the base config file, too.
  This is needed when we change configuration and want to save it.
- make Main pass "why3 <command>" as argv[0]
- remove "-version" options from everything but the main executable

Also:
- don't count "" and "contraption" as available commands
- pass every option except the command name to the command
- provide an option for extended help message

  This is to prevent quantified records from being decomposed by
  eval_match. e.g, assert { forall x:t. ... } was previously
  transformed to assert { forall x1:t1, x2:t2, x3:t3. ... } if x was
  a record type with fields x1,x2,x3. This changed the
  instantiation pattern, which could be harmful.

Also be more consistent when using stdout/stderr.

two parts: why3 and why3session.

(The Coq tactic does not include why3session)