Deprecate vs. discourage

[Ludovic Courtès]

Hello!

I think things like ‘uniform-vector-read’ should be discouraged rather
than deprecated, since it matches the definition in ‘discouraged.h’:

   A discouraged feature is one that shouldn't be used in new code
   since we have a better alternative now.  However, there is nothing
   wrong with using the old feature, so it is OK to continue to use
   it.

However, discouraged features currently don’t produce any sort of
warning.  I would suggest using the same technique as
‘build-aux/link-warning.h’ to issue a link-time warning.

What do you think?

Thanks,
Ludo’.