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

test/language/statements/break/12.8-1.js

test/language/statements/continue/12.7-1.js

test/language/statements/for-in/12.6.4-1.js

test/language/statements/for-in/12.6.4-2.js

test/language/statements/function/13.0-12-s.js

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

test/language/statements/function/13.2-1-s.js

test/language/statements/return/12.9-1.js

test/language/statements/variable/12.2.1-10-s.js

test/language/statements/variable/12.2.1-5-s.js

test/language/statements/variable/12.2.1-6-s.js

test/language/statements/with/12.10-0-1.js

test/language/statements/with/12.10-0-3.js

test/language/statements/with/12.10-0-8.js