Tests for RegExp dotAll proposal (#997)

test/built-ins/RegExp/S15.10.4.1_A5_T2.js

test/built-ins/RegExp/dotall/with-dotall-unicode.js

test/built-ins/RegExp/dotall/with-dotall.js

test/built-ins/RegExp/dotall/without-dotall-unicode.js

test/built-ins/RegExp/dotall/without-dotall.js

test/built-ins/RegExp/duplicate-flags.js

test/built-ins/RegExp/prototype/dotAll/length.js

test/built-ins/RegExp/prototype/dotAll/name.js

test/built-ins/RegExp/prototype/dotAll/prop-desc.js

...built-ins/RegExp/prototype/dotAll/this-val-invalid-obj.js

test/built-ins/RegExp/prototype/dotAll/this-val-non-obj.js

...-ins/RegExp/prototype/dotAll/this-val-regexp-prototype.js

test/built-ins/RegExp/prototype/dotAll/this-val-regexp.js

test/built-ins/RegExp/prototype/flags/order.js

test/built-ins/RegExp/prototype/flags/s.js