In certain deployments it might be desirable to remove the User-Agent header from the SIP message.
Set the sofia profile parameter "user-agent-string" to "none" to suppress this header.
These codecs are non-free which creates issues for distributions, so
let's not require these by default to run our example configs. We can
add back in iLBC once we resolve the licensing situation with our
in-tree implementation.
Spencer Thomason