* Work out what module filenames should be in CMake, and give those to C++
* Compare just the module filenames instead of the full strings
* Deal with OSG trying to support both UTF-8 and system-eight-bit-code-page file paths on Windows.
* Add a comment complaining about the constexpr situation.
* Use a stub implementation when using static OSG - apparently we don't actually support mixing and matching static and dynamic OSG plugins even though OSG itself does.
It doesn't work yet due to osgDB::listAllAvailablePlugins returning a list of paths to dynamic libraries.
That means:
* the check fails when the required plugin is linked statically.
* we're going to have to do something to slice up the filenames.
* there'll probably be unicode errors when the OpenMW installation path isn't representable by the current eight-bit code page on Windows.
Alternatively, we can switch to listing the required file extension support, and use osgDB::Registry::instance()->getReaderWriterList() and each element's supportedExtensions() function, but I don't think we've actually got that list of extensions anywhere and it might get desynced with the existing list of plugins if we add more.
