This adds default/fallback logic to determine the b2 exec absolute path
as possible. It uses the arg0 and current dir or path to construct the
liekliest path.
fixes#25
This ports the minimal Jambase to native C++. This removes the need for
mkjambase and the Jambase files. To accomplish that it adds C++
utility wrapers around Jam language primitives. Which makes future
similar work much easier.