[e-acsl] fix segfault for example

This is not detected by Eva because:
"no assigns clause generated for function length because pointers as arguments is not yet supported"

src/plugins/e-acsl/tests/examples/functions_contiki.c

@@ -24,6 +24,7 @@ int main(void) {
   struct list node1, node2, node3;
   node1.next = &node2;
   node2.next = &node3;
+  node3.next = NULL;
   struct list *l = &node1;
   /*@ assert length(l) == 3; */;
 }

src/plugins/e-acsl/tests/examples/oracle/functions_contiki.res.oracle

 [e-acsl] beginning translation.
-[e-acsl] functions_contiki.c:28: Warning: 
+[e-acsl] functions_contiki.c:29: Warning: 
   no assigns clause generated for function length because pointers as arguments is not yet supported
-[e-acsl] functions_contiki.c:28: Warning: 
+[e-acsl] functions_contiki.c:29: Warning: 
   no assigns clause generated for function length_aux because pointers as arguments is not yet supported
 [e-acsl] translation done in project "e-acsl".
-[eva:alarm] functions_contiki.c:18: Warning: 
-  accessing uninitialized left-value. assert \initialized(&l->next);
+[eva:alarm] functions_contiki.c:29: Warning: 
+  function __e_acsl_assert_register_long: precondition data->values == \null ||
+                                                       \valid(data->values) got status unknown.
+[eva:alarm] functions_contiki.c:29: Warning: assertion got status unknown.

src/plugins/e-acsl/tests/examples/oracle/gen_functions_contiki.c

@@ -41,6 +41,8 @@ int main(void)
   node1.next = & node2;
   __e_acsl_initialize((void *)(& node2.next),sizeof(struct list *));
   node2.next = & node3;
+  __e_acsl_initialize((void *)(& node3.next),sizeof(struct list *));
+  node3.next = (struct list *)0;
   struct list *l = & node1;
   __e_acsl_store_block((void *)(& l),8UL);
   __e_acsl_full_init((void *)(& l));
@@ -57,7 +59,7 @@ int main(void)
     __gen_e_acsl_assert_data.pred_txt = "length(l) == 3";
     __gen_e_acsl_assert_data.file = "functions_contiki.c";
     __gen_e_acsl_assert_data.fct = "main";
-    __gen_e_acsl_assert_data.line = 28;
+    __gen_e_acsl_assert_data.line = 29;
     __e_acsl_assert(__gen_e_acsl_length_here_2 == 3L,
                     & __gen_e_acsl_assert_data);
     __e_acsl_assert_clean(& __gen_e_acsl_assert_data);
@@ -90,7 +92,6 @@ long __gen_e_acsl_length_aux_here(struct list *l, unsigned int n)
       long __gen_e_acsl_if;
       if (n < 2147483647U) {
         long __gen_e_acsl_length_aux_here_3;
-        /*@ assert Eva: initialization: \initialized(&l->next); */
         __gen_e_acsl_length_aux_here_3 = __gen_e_acsl_length_aux_here
         (l->next,n + 1U);
         __gen_e_acsl_if = __gen_e_acsl_length_aux_here_3;