String.prototype.trimEnd,trimStart: add feature (per new convention)

...s/String/prototype/trimEnd/this-value-symbol-typeerror.js

...ilt-ins/String/prototype/trimEnd/this-value-whitespace.js

test/built-ins/String/prototype/trimStart/length.js

test/built-ins/String/prototype/trimStart/name.js

test/built-ins/String/prototype/trimStart/prop-desc.js

...uilt-ins/String/prototype/trimStart/this-value-boolean.js

.../String/prototype/trimStart/this-value-line-terminator.js

...tring/prototype/trimStart/this-value-not-obj-coercible.js

...built-ins/String/prototype/trimStart/this-value-number.js

...tart/this-value-object-cannot-convert-to-primitive-err.js

...otype/trimStart/this-value-object-toprimitive-call-err.js

...otype/trimStart/this-value-object-toprimitive-meth-err.js

.../trimStart/this-value-object-toprimitive-meth-priority.js

...Start/this-value-object-toprimitive-returns-object-err.js

...rototype/trimStart/this-value-object-tostring-call-err.js

...rototype/trimStart/this-value-object-tostring-meth-err.js

...ype/trimStart/this-value-object-tostring-meth-priority.js

...rimStart/this-value-object-tostring-returns-object-err.js

...prototype/trimStart/this-value-object-valueof-meth-err.js

...type/trimStart/this-value-object-valueof-meth-priority.js