[asterisk-dev] [Code Review]: Add a SIP nat=auto setting

[Terry Wilson]

> If we continue to not do combinable options, then we would have:
> 
> nat=no
> nat=force_rport
> nat=comedia
> nat=yes
> nat=auto_force_rport
> nat=auto_force_comedia
> nat=auto ; to be consistent with the nat=yes for combining the
> non-auto options

Of course, since it is trunk, we could also just rip everything apart and do something like:

nat_force_rport=on/off/auto
nat_comedia=on/off/auto

We could keep legacy settings around, but something like this would be a lot cleaner.