Also adds some comments.

On nested loops, for each iteration of the outer loop, postpone the widening of
the inner loop of [delay] iterations, [delay] being set by -eva-widening-delay.

Example:

while (i < n) {
  j = 0;
  while (j < 100) { j++; }
  i++;
}

On such nested loops, the fixpoint of the inner loop is independent from the
outer loop.

At the first iteration of the outer loop, a fixpoint is reached for the inner
loop. For other iterations of the outer loop, only one iteration of the inner
loop is needed to reach a new fixpoint, by only updating the variables modified
by the outer loop (i here). Avoiding widening during this one iteration is
crucial for precision, as the widening of the inner loop would widen the
variable i, leading to an overflow alarm at i++.

This can happen when copy of indeterminate bits are allowed, and the result
is uninitialized or escaping.

- Fix Value/Value#5
- Fix Value/Value#14

[Ptests] preserve LOG after STDOPT directive

See merge request frama-c/frama-c!2073

This is absolutely not a sneaky attempt to relaunch a build (now that OCI seems
in better shape) pushing a nearly empty commit.