new goals are associated to old goals directly in the order they appear.
they are all marked obsolete, unless the theory itself is found non
obsolete (thanks to the new checksums for theories)

in other words, reloading a session on a file that did not change results
in non-obsolete goals, even if checksums and shapes are absent (e.g. if
the file was not put under version control)

and merge the why3 and why3session libraries back into one.

check-sums from session in a near future, providing we can compute
check-sum of a while set of files, or of individual file,
or individual sessions (the latter more likely).

  because it is not part of the content of the file, and disallows
  simple diffing

two parts: why3 and why3session.

(The Coq tactic does not include why3session)

grants a long-standing feature wish by Andrei

          fix: recompute_all_shapes forgot to iter on metas