[libcxx] r260514 - Teach __hash_table how to handle unordered_map's __hash_value_type.

[Duncan P. N. Exon Smith via cfe-commits]

(For anyone else trying to line up this commit message with the
patch: it looks like this message is a dup of r260513, and this
patch is one of its described follow-ups:

> On 2016-Feb-11, at 04:25, Eric Fiselier via cfe-commits <cfe-commits at lists.llvm.org> wrote:
> 
> The following changes are planed for future revisions:
> 
>  * Fix LWG issue #2469 by delegating 'unordered_map::operator[]' to use
>    '__emplace_unique_key_args'.

^ This one.)