Merge pull request #350 from pvginkel/missing-features-on-es6-string-functions

...ring/prototype/endsWith/String.prototype.endsWith_Fail.js

...ng/prototype/endsWith/String.prototype.endsWith_Fail_2.js

...g/prototype/endsWith/String.prototype.endsWith_Success.js

...prototype/endsWith/String.prototype.endsWith_Success_2.js

...prototype/endsWith/String.prototype.endsWith_Success_3.js

...prototype/endsWith/String.prototype.endsWith_Success_4.js

...ype/includes/String.prototype.includes_FailBadLocation.js

...totype/includes/String.prototype.includes_FailLocation.js

...e/includes/String.prototype.includes_FailMissingLetter.js

...g/prototype/includes/String.prototype.includes_Success.js

...e/includes/String.prototype.includes_SuccessNoLocation.js

...rototype/includes/String.prototype.includes_lengthProp.js