Add support for OpenBSD
Allow the defining of an init file at build time

Since OpenBSD is unable to determine the pathname of a running process,
this allows us to specify the full path to flisp.boot. This will also
come in handy for system wide installs where you want flisp to live in
bin and flisp.boot to live in share or a similar location.
Merge pull request #8 from jturner/master

Adds support for OpenBSD and INITFILE define