By applying sed -i 's/tests\/non-free\//tests\/builtins\//g'

The source location of a precondition is at the call site.
When a behavior contains several unnamed preconditions, inlines preconditions
in the message to desambiguate them.

To avoid excessively long spaces when using long category names

Some state variables used in the specification of some functions were not
declared as extern, which is problematic for E-ACSL. They are only used to
provide correct specifications, but their actual value is not currently used.

Other changes:
- do not check for indeterminate values when assigning return code
  (problem with infinite values)
- two bugs :
  - t[v] = v when v is volatile (see Value/Value#68)
  - dangling value is not checked in return code (next commit)

Because of mutable weak bases, we cannot reuse the compositional book to
compute the cardinality.  Indeed, a base may change from strong to weak, and
the compositional bool cannot change in a synchronous way.