Fix build on Node 12+

[mattcollier]

This module is no longer building on node 12+

See: https://travis-ci.org/github/digitalbazaar/rdf-canonize/builds/731728025

[dmfilipenko-affinidi]

Hey @mattcollier, thanks for awesome work. Any plans to fix this issue? Do you need any help with this?

[mattcollier]

@dmfilipenko-affinidi Hello, this module was created at a time when this native implementation was more performant than JS. This module has fallen into disuse since the JS/V8 implementation caught up performance wise.

[danbri]

Maybe a WASM build would fill whatever gap is left?

[davidlehn]

@danbri If someone is interesting in tackling this, I'd suggest first building the native code on an older Node.js, and benchmarking that against the pure js version on a modern Node.js. I have no idea what the result will be. I'd put my money on about even or a js edge. ;-)

Someone with more experience with the modern native API could probably update this code fairly quickly too.

I'd also suggest revisiting benchmarks and profiling on the pure js code before going to far down the native code route. There might be algorithmic gains there for less effort. (There's at least one outstanding patch for a small optimization.)