Rename p_free_tree() to p_tree_delete()

spec/test_tree.c

@@ -33,7 +33,7 @@ int main()
     assert_eq(22, itemsmore->pItem->pToken1->pvalue);
     assert(itemsmore->pItemsMore == NULL);
 
-    p_free_tree(start);
+    p_tree_delete(start);
     p_context_delete(context);
 
     input = "";
@@ -42,7 +42,7 @@ int main()
     start = p_result(context);
     assert(start->pItems == NULL);
 
-    p_free_tree(start);
+    p_tree_delete(start);
     p_context_delete(context);
 
     input = "2 1";
@@ -57,7 +57,7 @@ int main()
     assert(start->pItems->pItem->pDual->pTwo2 == NULL);
     assert(start->pItems->pItem->pDual->pOne1 == NULL);
 
-    p_free_tree(start);
+    p_tree_delete(start);
     p_context_delete(context);
 
     return 0;