bug#15405: 24.3; #[] freezes emacs

[Drew Adams]

>> Perhaps (eval #[]) should evaluate to [] instead of #[]?
>
> An alternative is to fix the counter intuitive fact that (eq [] [])
> is t. Doing so could break Elisp code that relies on the behavior, and
> possibly impact performance.

FWIW, this behavior was introduced only recently: 24.3.  It is true for
only this one Emacs release (so far).  It is an incompatible change from
Emacs prior to 24.3, where (eq [] []) is nil.