The ported test for lib.string::operator+ is here:
http://people.apache.org/~antonp/stdcxx05182006/

Also there are required changes to 21.strings.h/cpp files: 5 new
signatures and memberId element, etc.

But we are going to run out of bits in the MemberId enumeration, and it
blocks the rest of the tests porting.
I think we may transform the overloadId to the structure with 2 fields:
memberId and signatureId. 
I can implement this if you agree. What do you think about this?

Also there is another question: shall we keep all non-members tests in
one cpp file or in several files like for the find methods done?

Thanks,
Anton Pevtsov