Allow underscores in DNS names

[Terry Lambert]

Dag-Erling Smørgrav wrote:
> The attached patch, inspired by a discussion on -STABLE, modifies our
> resolver library to allow underscores in host names, by classifying
> the underscore as a hyphen character.  Even though RFC952 forbids
> them, underscores are becoming increasingly common in DNS, and they
> are sometimes used for mechanisms (such as Microsoft's automatic proxy
> configuration scheme) which we might want to support in FreeBSD.


There was a better patch that made it an option in resolv.conf,
rather than turning it on all the time.

FreeBSD should be standards compliant, by default, and take work
to make it possible to give bogus data to other hosts on the
Internet who can not handle "_" or other characters because they
*are* standars compliant.

"Be conservative in what you send."

-- Terry