[janitor patch] Drop vestiges of 14-character limit support

[DJ Delorie]

> If this is used in a host which simply hasn't been integrated yet (but is
> hoped to be integrated soon), by all means someone should tell me and I'll
> drop the patch.

We already have plenty of reasons why such hosts won't work anyway.

> 	* configure.in: Remove references to host_truncate_target.
> 	* configure: Regenerate.
> 	* config.gcc: Remove references to truncate_target,
> 	host_truncate_target.

Ok.