emplace method for associative containers

[Rodolfo Lima]

Hi, it seems that the emplace method (C++0X) is missing from associative 
containers like sets, multisets, unordered_sets, etc. This method is 
currently implemented for sequence containers but IMHO it's more useful 
in context of unique associative containers in that the object is only 
created if the insertion will take place, whereas in sequence container 
the object is always created and inserted, which can be accomplished 
solely by the insert method.

Regards,
rod