Fixes #617

Technically, the C standard distinguishes between declarations and statements,
and only the latter may have labels attached to them. Thus, printing a label
directly over a `Local_init` will result in ill-formed C code. In order to
avoid that, we add a dummy nop (aka `;`) in-between.

A first version was done in !1518, but failed to take into account
`UnspecifiedSequence` whose first element happens to be a `Local_init` 

- 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.