These warnings are emitted when a garbled mix is written through an
assignment or an assigns clause.
This commit:
- rephrases the warnings to be clearer and less verbose.
- emits the warning only for garbled mix created at the current statement,
  according to their origin. Do not emit warnings for each propagation of
  previous garbled mixes.
- emits the warning when assigning garbled mix to the formal parameters
  of a function from the arguments of a call.

In all files, all occurrences of "[eva] done for function" have been replaced
by "[eva] Done for function".

New smart constructor for TCastE in logic_const.

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

Some case studies (e.g. dyad) use some ugly casts from fd_set_t which lead
to the analysis stopping too early.
Changing the representation of fd_set_t should also help it better conform to
the standard (since a fd_set_t should be able to hold FD_SETSIZE elements).

[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.