Minor multi threading improvement

MTMode 1 is now tested, which means 2 and higher works as well.
Thus the plugin should work no matter the MT level the user has configured for the overall script.

Note that the plugin itself is rather quick, about 50% overhead compared to just reading raw frames using FFMS2, and as such, using MT gains very little for this plugin.

Support for 64bit and VapourSynth

This is a minor update which offers support for windows 64bit Avisynth players, as well as VapourSynth.

For convenience, the binaries are now offered on Github, along with the source.

To build from source, one needs from now on to build the plugin from the Visual Studio GUI, since microsoft has stopped supporting command line builds using nmake. Thereby also putting an end to any notion of being able to offer automated and verifiable builds using a CI pipeline.