The RegExp named groups specification has changed to not throw
errors in certain cases. This patch updates the test262 tests to match
the new specification, and throws in an additional test that verifies
the interaction between named group syntax and other replacement.
The tests pass on a version of V8 which implements the new semantics.

https://github.com/tc39/proposal-regexp-named-groups/commit/92ceba518c2ab0d2811c2efa8248ed1b3f8b5506