Bug#956200: gimp: remove old-style config script `libwmf-config'

[Simon McVittie]

On Wed, 08 Apr 2020 at 13:20:35 +0200, Andreas Henriksson wrote:
> Possibly things should be refactored to *first* try pkg-config and
> then fall back on looking for the libwmf-config script

I think that's a better approach, and I've implemented it.
https://gitlab.gnome.org/GNOME/gimp/-/merge_requests/319
If accepted upstream, that might be a useful template for other dependent
packages.

    smcv