build failure due to observer.sh

[Joel Brobecker <brobecker@gnat.com>]

Hello,

The build failed on most of our machines, due to a problem happening
during the sed command in observer.sh. Here is the output we got:

        Creating observer.h-tmp
        sed:     # Save original line for later processing into the actual parameter is not a recognized function.

As a consequence, all observers are missing, and we fail during the link.

I tried on AiX to remove the comments, to see if it works any better,
and managed to get past this error. Are comments a GNU sed extension?

In my opinion, I would handle observer.sh the same as gdbarch.sh:
The contributors run it manually when needed. And we keep and up-to-date
version of observer.[hc] checked in the repository. That way, we avoid
requiring a certain implementation of sed when just building GDB.

I can regenerate observer.[hc] and check them in, if you agree.

-- 
Joel