New heuristics for MCF algorithms (#340)
and some implementation improvements.

- A useful heuristic is added to NetworkSimplex to make the
initial pivots faster.
- A powerful global update heuristic is added to CostScaling
and the implementation is reworked with various improvements.
- Better relabeling in CostScaling to improve numerical stability
and make the code faster.
- A small improvement is made in CapacityScaling for better
delta computation.
- Add notes to the classes about the usage of vector<char> instead
of vector<bool> for efficiency reasons.

EXTRA_DIST += \

	scripts/bib2dox.py \

	scripts/bootstrap.sh \

	scripts/chg-len.py \

	scripts/mk-release.sh \

	scripts/unify-sources.sh \

	scripts/valgrind-wrapper.sh