sth.js: added a couple of test helper functions

test/harness/sth.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-b-1.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-b-2.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-c-1.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-c-2.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-d-1.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-d-2.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-d-3.js

...uite/ietestcenter/chapter11/11.1/11.1.5/11.1.5_4-4-d-4.js

.../suite/ietestcenter/chapter11/11.4/11.4.1/11.4.1-4.a-5.js

.../suite/ietestcenter/chapter11/11.4/11.4.1/11.4.1-4.a-7.js

test/suite/ietestcenter/chapter15/15.10/15.10.6/15.10.6.js

...stcenter/chapter15/15.10/15.10.7/15.10.7.1/15.10.7.1-1.js

...stcenter/chapter15/15.10/15.10.7/15.10.7.2/15.10.7.2-1.js

...stcenter/chapter15/15.10/15.10.7/15.10.7.3/15.10.7.3-1.js

...stcenter/chapter15/15.10/15.10.7/15.10.7.4/15.10.7.4-1.js

...stcenter/chapter15/15.10/15.10.7/15.10.7.5/15.10.7.5-1.js

...stcenter/chapter15/15.2/15.2.3/15.2.3.3/15.2.3.3-4-178.js

...stcenter/chapter15/15.2/15.2.3/15.2.3.3/15.2.3.3-4-179.js

...stcenter/chapter15/15.2/15.2.3/15.2.3.3/15.2.3.3-4-180.js