Prior to this patch, two distinct failure cases would produce the same
generic error message. Refactor the test logic to report the specific
condition which trigger failure.
* Move decimalToHexString into harness instead of duplicating it in multiple files
* Optimize decimalToHexString and support numbers greater than 65535
* Replace alternative decimalToHexString function with include for decimalToHexString.js
* Add decimalToHex2String to return the string representation of a two-digit hex-number
* Replace decimalToHex2String with decimalToPercentHexString to return the percent hex-encoded string of a two-digit hex-number
* Replace two String.fromCharCode calls with a single call
* Further reduce string concatentations in decodeURI[Component] tests
* Remove unnecessary Test262Error error handling in catch-clauses
* Remove try/catch wrappings in decodeURI/encodeURI tests
