Replace runTestCase with assert helpers [test/language/statements]

test/language/statements/function/13.0-17-s.js

test/language/statements/function/13.0-8-s.js

test/language/statements/function/13.1-1-1.js

test/language/statements/function/13.1-1-2.js

test/language/statements/function/13.1-2-1.js

test/language/statements/function/13.1-2-5.js

test/language/statements/function/13.1-2-6.js

test/language/statements/function/13.1-3-1.js

test/language/statements/function/13.1-3-2.js

test/language/statements/function/13.1-3-7.js

test/language/statements/function/13.1-3-8.js

test/language/statements/function/13.2-11-s.js

test/language/statements/function/13.2-12-s.js

test/language/statements/function/13.2-15-s.js

test/language/statements/function/13.2-16-s.js

test/language/statements/function/13.2-19-s.js

test/language/statements/function/13.2-20-s.js

test/language/statements/function/13.2-23-s.js

test/language/statements/function/13.2-24-s.js

test/language/statements/function/13.2-27-s.js