Cut a release of 0.X to support a homebrew formula for libsecp256k1

[rickmark]

Hello,

Today we have the ability to install libbitcoin and other core bitcoin libraries via homebrew but it builds and installs libsecp256k1 as a private library. I'm working both on moving libsecp256k1 to it's own formula so it can be used independently of libbitcoin as well as ruby-secp256k1 as native bindings for Ruby. In order to support this we need to be able to refer to a cut release of libsecp256k1. While I understand that it is not v1 yet, cutting a v0.8 or v0.9 for the non-experimental modules of core, ecdh, and recovery would enable wider adoption and contributions to this library.

The ask is to create a pre v1 release for homebrew.

[rickmark]

Proposed homebrew formula

libsecp256k1.rb.txt

[real-or-random]

Hey. Strictly speaking this is a duplicate of #286, and we should continue the discussion there.

I admit that referring you to a six years old issue is not really satisfactory. I think there's no compelling reason not to tag a pre-release. We just need to spend the time to do it. See also #856, any comments there will help.