These macros should make the diffs more understandable and maintainable.

Also fix assertion from test in strchr.

Boris Yakobowski authored 7 years ago and David Bühler committed 7 years ago

Instead, include the proper libc headers, with the specifications.
Otherwise, in the next commits(s), we won't have preconditions to evaluate, and the tests
will be come unsound

Changes:

- share/libc/stdlib.c: previous version of calloc in stdlib. used Frama_C_memset, which is idiotic since
  - for non-free we now *have* a builtin for calloc
  - stdlib.c is meant for people with non-free builtins

- same thing for tests/libs/string_c.c: the builtin was used

- nonfree/imprecise.c:
  sizeof(v3), where v3 is an abstract struct, is evaluated slightly less precisely now.
  We don't care as long as it does not crash.

- nonfree/strchr.c:
  the test is buggy, the behavior was undefined

Each call to fold_itv must be preceded by a check of the actual validity of
the offsets (since fold_itv will take the intersection). In the case of an
exact offset, the right side is already taken into account, so we only have
to check the left (negative) bounds.