configure: automatic dependencies for plugins
configure: automatic dependencies for plugins

Now configure will die when libass, imagemagick, or tesseract are
missing only if the corresponding plugin was explicitly enabled (with
--enable-plugins or with its own switch).

vapoursynth/vapoursynth,Kamekameha/vapoursynth,vapoursynth/vapoursynth,vapoursynth/vapoursynth,Kamekameha/vapoursynth,vapoursynth/vapoursynth,Kamekameha/vapoursynth,Kamekameha/vapoursynth