The only plugins remaining are those that haven't been ported to Meson yet, and msdk. Also, the tests are still automagic. https://bugzilla.gnome.org/show_bug.cgi?id=795107
https://bugzilla.gnome.org/show_bug.cgi?id=794568
This patch bumps the required meson to 0.40.1 as gstreamer core just did, and cleanup some code to use a feature from 0.37 that allow specifying version range when checking dependency. https://bugzilla.gnome.org/show_bug.cgi?id=780654
