Hello everyone,

Here is something that implements a compromise between the previous
behavior, and the new behavior in terms of objfile search order.

The gist of the patch is that it introduces an iterator that can
take a "context" objfile into account for the iteration order.
The rest are small adjustements to use the iterator. Long term,
I think we are opening the door for more arch-dependency by
adjusting the body of the iterator. I'll leave that part to someone
else who's motivated (I think it's a can of worms).

This patch assumes that my other patch has been reverted.  This way,
it allows us to start from the initial code, and see how I am
changing it this time.

It also includes a C testcase, which hopefully reproduces the same
issue as gdb.fortran/library-module.exp, but in C, to widen the
number of people testing this feature.

For now, it's only a prototype, so I'm seeking comments. I will
document the code when we're happy with the approach.

Tested on x86_64-linux, no regression. Fixes the new testcase.

Thanks,
-- 
Joel