Fix memory leak by adding "owner" concept of node

src/hydroforth/interpreter.c

@@ -7,6 +7,11 @@
 
 void free_word_def_value(void *x) {
   struct hf__interpreter__word *word = x;
+
+  for (size_t i = 0; i < word->body_len; i++) {
+    // TODO: free nodes
+  }
+
   free(word->body);
   free(word);
 }
@@ -54,17 +59,12 @@ struct hf__result words__word(struct hf__interpreter *const interpreter,
     hf__parser__node_array_push(
         &interpreter->call_stack, &interpreter->call_stack_len,
         &interpreter->call_stack_size, (*word)->body[i]);
+    interpreter->call_stack[interpreter->call_stack_len - 1].is_owner = false;
   }
 
-  /* FIXME: Word name points to copy of pointer of original name,
-    when cleared here all other references loose access to the pointer's value
-    => SIGSEV!
-
-    For now I am going to ignore the memory leak.
-    Copying the word name may be a better option but is pretty memory
-    inefficient.
-  */
-  // free(node->value.word.value);
+  if (node->is_owner) {
+    free(node->value.word.value);
+  }
 
   return HF__OK;
 }