[analysis-scripts] improve the ability to benchmark eva runs

See merge request frama-c/frama-c!2114

[Analysis-scripts] add find-fun script, to grep for function declarations/definitions

See merge request frama-c/frama-c!2086

merlin for external plugins

See merge request frama-c/frama-c!2096

[lib/json] adopt Yojson.Basic type

See merge request frama-c/frama-c!2104

[aorai] remove obsolete release target from Aoraï's Makefile.

See merge request frama-c/frama-c!2061

[Eva] Minor rewriting of the bitwise operators

See merge request frama-c/frama-c!2101

[Eva] Uses enumerate_valid_bits instead of enumerate_bits.

See merge request frama-c/frama-c!2084

[Eva] Improves widenings on nested loops

Closes Value/Value#122 and Value/Value#123

See merge request frama-c/frama-c!2046

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++.