Eva relies on the inout plugin to ensure that a function call has not modified
the values of its concrete arguments, meaning that at the end of the call, the
values of formal parameters can be backward propagated to the corresponding
concrete arguments. This is useful when the values of some parameters have been
reduced by the call, for instance by some preconditions.

To this end, Eva uses the Inout callback Record_Inout_Callbacks from Db, but
this callback was only applied by Inout for functions whose body is analyzed.

This commit modifies Inout to also record its result through this callback
on functions interpreted by a builtin or a specification, thus allowing a
precise backward propagation of the values of formal parameters to concrete
arguments in all cases.

- always remove FC's internal attribute everywhere before deciding whether
  a cast is needed.
- ACSL and C decisions to cast are similar
- only unroll type for checking equality. If a cast is needed, keep
  typedef (if any) as target

attributes that are completely internal to Frama-C and do not have any impact
on the semantics of the underlying value should not lead to a cast node.

These tests have missing specs, so the large amount of warnings is expected.

There are still many missing specifications, but at least parsing should
succeed for strictly POSIX-compliant code.

Frama-C does not yet support _Alignof and _Alignas, but this header helps
parsing code and emitting a proper error message.

Clang 13 emits warnings related to uninitialized variables:

variable 'r' is used uninitialized whenever 'if'
condition is false [-Wsometimes-uninitialized]

This is due to the fact that the assert(0) macro, when using Frama-C's libc,
is expanded to __FC_assert. Since it is not known by the compiler, it cannot
consider it as "noreturn" when the condition is zero. Note that adding
'__attribute__ ((__noreturn__))' will not work: Frama-C will assume it
never returns, even when the condition is true.
Initializing the 'r' variables with a default value will not change the
actual behavior, and will avoid the warnings.