Fixes [external BTS 2432](https://bts.frama-c.com/view.php?id=2432)

Fixes external issue 2433

As it is redundant with all the information displayed during the analysis.

This can notably reduce the possible number of iterations after a widening.

And not each time the option is changed.

As this can reset all saved states. Modified options will be set to their proper
values anyway.

Only keeps -eva-precision.
-eva-precision changes the paramaters even if they have already been set.
-eva-precision -1 resets the options to their default value.

Quick configuration of a fast (but imprecise) or precise (but slow) analysis.

This module type simplifies the signature of functors using evaluation
functions.

Do not call enter_scope and leave_scope when no variables enter or leave the
scope.

Fixes a performance issue.

Fixes a performance issue.

The extraneous include prevents gzip from compiling.

- shares and moves the functions [reduce_offset_by_validity] of Locations and
  Precise_locs into base.ml.
- replaces the boolean argument ~for_writing into the new type access, that
  represents Read, Write or No_access. Without any access, offsets must point
  into or just beyond the base validity.
- fixes the support of accesses of size 0: they are now invalid:
  + in bases with Invalid validity;
  + one past a base validity unless the base ends with an empty struct.

If needed, this boolean could be computed by the callers of these functions via
Base.is_valid_offset.
In Base, do not export offset_is_in_validity, that was only used to compute
this boolean.

Since commit #8783731f and #28139960 this option is not needed anymore.
I updated LUncov (which was the only plugin using it) to remove it as well

Do not use two distinct undo stacks for taking care of which symbols are in use
at a given program point. Let `Alpha` manages everything internally.