Add a cost scaling min cost flow algorithm.

Add a cost scaling algorithm, which is performing generalized
push-relabel operations. It is almost as efficient as the capacity
scaling algorithm, but slower than network simplex.

 EXTRA_DIST += \

 	tools/Makefile

 if WANT_TOOLS

 bin_PROGRAMS += \

 	tools/dim_to_lgf \

 	tools/lgf-gen

 endif WANT_TOOLS

 tools_lgf_gen_SOURCES = tools/lgf-gen.cc

 tools_dim_to_lgf_SOURCES = tools/dim_to_lgf.cc