Add a record with 2 fields : tnode and tattr

Returns `Bottom when needed, instead of using V.bottom.

- now, its a single constructor
- also adds a boolean logic constant

No need to reset the current location after the analysis of a function or
after calling a visitor, as the new API ensures that this is the case.

David Bühler authored 1 year ago and Allan Blanchard committed 1 year ago

- Only generates assigns clauses when required:
  - when the analysis uses the specification to analyze a function
    (decided in function_calls.ml)
  - for Frama_C_* builtins, such as Frama_C_assert. Others builtins should
    already have a specification.
  - when interpreting a Frama_C_show_each directive, so other plugins known
    these functions have no effect.
  - in [Logic_inout.valid_behaviors], used by inout and from plugins to
    interpret a function specification.

- Also generates assigns clauses for functions with a body: this is required
  for the analysis of recursive functions and of functions specified in the
  -eva-use-spec parameter (in both case, a specific Eva warning is emitted).

- In recursion.ml, renames get_spec to check_spec.
  The generation of assigns clauses is now uniformly done in function_calls.

And no longer the cvalue initial state normally computed by the analysis,
when no initial state is supplied externally.
The initial cvalue state can always be accessed from Cvalue_results.

Removes [initial_state_only_globals] from Db.Value.

New file cvalue_results storing the cvalue states (using Domain_store.Make).