WIP: Support user data within container.

It is useful for calling methods with another user data argument.
It is mainly useful for custom allocations,
so for now, only custom allocations methods can access the user data.
Port it to array container.

README.md

@@ -622,7 +622,7 @@ Other documented operators are:
 * KEY\_OPLIST() --> oplist: Return the oplist of the key type for associative containers.
 * VALUE\_OPLIST() --> oplist: Return the oplist of the value type for associative containers.
 * NEW (type) -> type pointer: allocate a new object (with suitable alignment and size) and return a pointer to it. The returned object is **not initialized** (a constructor operator shall be called afterward). The default method is M\_MEMORY\_ALLOC (that allocates from the heap). It returns NULL in case of failure.
-* DEL (&obj): free the allocated uninitialized object 'obj'. The object is not cleared before being free (A destructor operator shall be called before). The object shall have been allocated by the associated NEW method. The default method is M\_MEMORY\_DEL (that frees to the heap).
+* DEL (&obj): free the allocated uninitialized object 'obj' given its type pointer. The object is not cleared before being free (A destructor operator shall be called before). The object shall have been allocated by the associated NEW method. The default method is M\_MEMORY\_DEL (that frees to the heap).
 * REALLOC(type, type pointer, number) --> type pointer: realloc the given array referenced by type pointer (either a NULL pointer or a pointer returned by the associated REALLOC method itself) to an array of the number of objects of this type and return a pointer to this new array. Previously objects pointed by the pointer are kept up to the minimum of the new size and old one. New objects are not initialized (a constructor operator shall be called afterward). Freed objects are not cleared (A destructor operator shall be called before). The default is M\_MEMORY\_REALLOC (that allocates from the heap). It returns NULL in case of failure in which case the original array is not modified.
 * FREE (&obj) : free the allocated uninitialized array object 'obj'. The objects are not cleared before being free (CLEAR operator has to be called before).  The object shall have been allocated by the associated REALLOC method. The default is M\_MEMORY\_FREE (that frees to the heap).
 * INC\_ALLOC(size\_t s) -> size\_t: Define the growing policy of an array (or equivalent structure). It returns a new allocation size based on the old allocation size ('s'). Default policy is to get the maximum between '2*s' and 16. NOTE: It doesn't check for overflow: if the returned value is lower than the old one, the user shall raise an overflow error.