Initial socket SMACK label caching

Preliminary code to read and cache the SMACK label of the connected client socket, if it exists.

Also adding configure option to specify the load file location (and a sample load2 file) for testing on systems that do not have SMACK enabled.

Not failing right now if no SMACK label is found, since I'm not really sure I'm doing this in the right place or way yet.  Looking for feedback... thanks.