Warn when using shuffle(...) on checked map arrays

Summary: The ##shuffle(...)## builtin destroys keys so it should raise a warning when
operating on a checked map array.

Reviewed By: @paroski

Differential Revision: D1489727
Introduce async function lambdas

Summary: Introduce lightweight way to define async function closures. Adds ability to prepend lambda functions with async keyword.

It also works with async generators!

Reviewed By: @billf

Differential Revision: D1402430
Added ext/reflection tests

Summary: This diff un-blacklists ext/reflection tests and imports them

Reviewed By: @fredemmott

Differential Revision: D1489330
Added ext/gmp tests

Summary: This diff un-blacklists ext/gmp tests and imports them

Reviewed By: @fredemmott

Differential Revision: D1489612
Imported ext/tokenizer tests

Summary: This diff un-blacklists ext/tokenizer tests

Reviewed By: @fredemmott

Differential Revision: D1489306
Added ext/dom php tests

Summary: This diff un-blacklists ext/dom tests and imports them

Reviewed By: @fredemmott

Differential Revision: D1489744