Replace p_context_init() with p_context_new()/p_context_delete()

spec/test_tree_field_aliases.d

@@ -10,10 +10,10 @@ int main()
 unittest
 {
     string input = "\na\nb\nc";
-    p_context_t context;
-    p_context_init(&context, input);
-    assert(p_parse(&context) == P_SUCCESS);
-    Start * start = p_result(&context);
+    p_context_t * context;
+    context = p_context_new(input);
+    assert(p_parse(context) == P_SUCCESS);
+    Start * start = p_result(context);
 
     assert_eq(TOKEN_a, start.first.pToken.token);
     assert_eq(TOKEN_b, start.second.pToken.token);