Enable profiling / leak detection in FreeBSD

* Assumes procfs is mounted at /proc, cf.
  <http://www.freebsd.org/doc/en/articles/linux-users/procfs.html>
Consistently use debug lib(s) if present

Fixes a situation where nm uses the debug lib but
addr2line does not, which completely messes up the symbol
lookup.
Consistently use debug lib(s) if present

Fixes a situation where nm uses the debug lib but
addr2line does not, which completely messes up the symbol
lookup.
Merge pull request #59 from HarryWeppner/dev

FreeBSD memory (leak) profiling support