[v3] Add segmented-iterator optimization for std::copy of deque::iterator ranges

[Paolo Carlini]

... and the below completes the work with the *_backward counterparts.

Tested x86_64-linux multilib, and testsuite/performance.

Paolo.

////////////////////////
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: CL_copy_backward_deque
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20091224/802b869c/attachment.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: patch_copy_backward_deque
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20091224/802b869c/attachment-0001.ksh>