[Plplot-general] findwxwidgets.cmake module

[Phil R. <p.d...@gm...>]

Hi Alan
I half thought that we had scrapped our findwxWidgets.cmake module,
but I just found that this isn't actually the case.

I've just disabled our version by renaming it, and I've found that the
CMake version does appear to work on Windows. This is using cmake
3.13.3 (the latest release as of writing this email).

I seem to remember that it was for windows builds that we were
maintaining our own version. Perhaps this can now be removed?

Phil