Attempting to build OpenBSD fails for various reasons.
First and foremost, there is a number of packages that have to
be installed as build dependencies
Than, small updates are needed to the autotools files to have autogen.sh
and configure, to exit without errors.
doc/README.OpenBSD describes the whole process in fair detail.
Last but not least, there are type errors that g++ compiler catches in
OpenBSD but not in Linux. To have the build, a few source files
were updated to have effect only in OpenBSD, leaving other operating
systems untouched.
With only one exception, a prototype in include/Flow.h was updated to
stay in sync with the implementation.
