curve25519

#283 fixes a few of them but I think there's more since the repo restructuring last year. I don't have access to the buckets hosting the http://doc-internal.dalek.rs pages, so I'm not able to update them.

The gem is presently not packaged in such a way it will build on non-x86 architectures.

It shouldn't be too hard as it already packages the portable ref10 implementation, but some work will be required in e.g. extconf.rb

While there are a number of build tags to try to force the no assembly and 32-bit backends to be build and exercised this really should build and test with an actual 32-bit toolchain/system so that stupid errors can be caught.

As we don't care about performance, QEMU or something should be sufficient here.