RegExp named group tests (#998)

...uilt-ins/RegExp/named-groups/functional-replace-global.js

...-ins/RegExp/named-groups/functional-replace-non-global.js

test/built-ins/RegExp/named-groups/groups-properties.js

test/built-ins/RegExp/named-groups/lookbehind.js

test/built-ins/RegExp/named-groups/non-unicode-malformed.js

test/built-ins/RegExp/named-groups/non-unicode-match.js

...ilt-ins/RegExp/named-groups/non-unicode-property-names.js

test/built-ins/RegExp/named-groups/non-unicode-references.js

test/built-ins/RegExp/named-groups/string-replace-get.js

test/built-ins/RegExp/named-groups/string-replace-missing.js

...uilt-ins/RegExp/named-groups/string-replace-nocaptures.js

.../built-ins/RegExp/named-groups/string-replace-numbered.js

.../built-ins/RegExp/named-groups/string-replace-unclosed.js

...built-ins/RegExp/named-groups/string-replace-undefined.js

test/built-ins/RegExp/named-groups/unicode-malformed.js

test/built-ins/RegExp/named-groups/unicode-match.js

test/built-ins/RegExp/named-groups/unicode-property-names.js

test/built-ins/RegExp/named-groups/unicode-references.js