std::map and std::set based on AVL, not RB trees.

[Paolo Carlini]

Jonathan Wakely wrote:

>Paolo, Chris, was the resolution to PR19433 the right one?
>  
>
Yes definitely it is, because we are simply implementing the exact text
of the current standard. DR 233 is in the *Open* status, a long way
before "TC" or even "Ready". Why are you suspecting something strange
going on?!?

Paolo.