Merge from pch branch; call for testers

[Geoff Keating]

> I guess I can reverse engineer what is required but a few hints or even
> some documentation would be very helpful. 

How about looking at the manual?  It's node "Type Information" in
gccint.info.

I do not recommend reverse-engineering.  The current gengtype.c is not
final and many parts of it are intended to be replaced in the future.
If an example is desired, I'd suggest looking at the changes to the
Fortran frontend, which is simple, and the C++ frontend, which isn't.

> It appears I will need to patch gengtype.c to add treelang to the hard
> coded list of languages (lang_names) included therein. Is there any
> alternative to this? Normally the determination of languages is by a
> discovery process rather than hard coding in sundry files.

Please feel free to suggest a patch.

-- 
- Geoffrey Keating <geoffk@geoffk.org> <geoffk@redhat.com>