port to POSIX capabilities API via libcap
Procenv currently uses prctl to get Linux process capabilities. This limits use to linux >= 2.6.25. Effect is no capabilities information on RHEL5, for example.
A more compatible / well-defined / backport-friendly alternative would be to use the POSIX capabilities API through the libcap or libcap-ng libraries. I can hack on this when I get a free moment, but let me know if you'd object to such a change.