Port preflow push max flow alg. from svn -r3516 (#176)
Namely,
- port the files
- apply the migrate script
- apply the unify script
- break the long lines in lemon/preflow.h
- convert the .dim test file to .lgf
- fix compilation problems

 if WANT_TOOLS

 bin_PROGRAMS +=

 dist_bin_SCRIPTS += tools/lemon-0.x-to-1.x.sh

 endif WANT_TOOLS