* crypto: Add benchmarking code for signature schemes
This does a slight refactor for the key generation code. It now calls a
seperate unexported method to allow generation from a reader. I think this
will actually reduce time in generation, due to no longer initializing an
extra slice. This was needed in order to enable benchmarking.
This uses an internal package for the benchmarking code, so that this can
be standardized without being exported in the public API. The benchmarking
code is derived from agl/ed25519's benchmarking code, and has copied the
license over.
Closes#1984