evolve: move builddependencies() and _singlesuccessor() to utility module
The builddependencies() and _singlesuccessor() function are very useful
functions and can be used at a lot of places. They are also used in topic
extension also, so let's move them to utility. However moving them to utility
won't help anything in the topic extension.
syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
^tests/.*\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes
^docs/training/graphs/
^docs/training/html/
^docs/training/index.html
^docs/training/graphviz-images/
^docs/training/img/
^docs/training/output/
^docs/training/pandocfilters/