[PATCH] Update backward/algo.h

[Paolo Carlini]

Nathan Myers wrote:

> OK, but be careful about hitting control-C during your build!
> (That goes for everyone, not just Paolo, until this gets fixed.)
> Was everybody else unfamiliar with the rule?  Maybe we need to
> audit the #includes in the standard headers.

Ah, now I see!
Don't worry about this: I have *not* yet applied my patch for backward/algo.h!
Of course I was waiting for approval.

Cheers,
Paolo.