Improvements in MinCostFlow and MinCostMaxFlow.

Main changes:
- MinCostMaxFlow also provides dual solution.
- Change the name of private members to start with "_".
- Change the name of function parameters not to start with "_".
- Remove unnecessary documentation for private members.
- Doc improvements.

#!/bin/bash

cd ${0%update-libstd-tag}../doc

mv libstdc++.tag libstdc++.tag.old

wget http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/libstdc++.tag &&

rm libstdc++.tag.old || mv libstdc++.tag.old libstdc++.tag