- Plugins fields in the AST are used to find the right extension
- A plugin still cannot register twice an extension
- If plugin is not given, can throw ambiguity error
- Kernel extensions are an exception, a plugin cannot register an
extension with the name name than the kernel

- Cil_types.acsl_extension
- Logic_ptree.extension & global_extension

[Libc] add some POSIX and non-POSIX constants

See merge request frama-c/frama-c!4792

Adds help to Eva message categories

See merge request frama-c/frama-c!4798

[kernel] Add optional description to keys

See merge request frama-c/frama-c!4780

[Libc] undefine 'index'/'rindex' if POSIX >= 200809

Closes #1422

See merge request frama-c/frama-c!4795

[kernel] fix pretty printing of assigns-from clauses

Closes #1398

See merge request frama-c/frama-c!4796

[Eva] Offsetmap: removes some feedback messages about approximations.

See merge request frama-c/frama-c!4777

In offsetmaps, removes a reference to change the feedback emitted when
approximating the write of large memory locations.

Instead, the main offsetmap functor takes an additional parameter about
whether such messages should be emitted. Only the offsetmaps build by the
Eva cvalue domain emits these messages, as write approximations may have a
significant impact on the analysis precision.
Offsetmaps used to represent memory zones or dependiencies do not emit
these messages, which were most often insignificant and instable
(as many plug-ins and Eva domains use memory zones in various ways).

[Kernel] avoid stacktrace and show more precise plugin loading error message

See merge request frama-c/frama-c!4754

[cabs2cil] Use CALL loc as vdecl for missing prototypes

See merge request frama-c/frama-c!4791