The future of cpuminer-opt.

A number of things are converging that require some decisions to be made.

After 7 years I think I've squeezed about as much juice from cpuminer as I can. I have a couple more small optimisations so there will be,
at least, one more release.

Another factor is I'm planning to upgrade my main system, where I build the Windows binaries package. That means I will need to rebuild
the mingw environment for Ubuntu-22.04 from scratch or build a Ubuntu-20.04 VM and port the existing environment to it.
Without a plan for more development it's hard to get motivated to do the extra work. There is also now a more friendly way for Windows users
to compile their own, and with better tuning for their CPU.

cpuminer-opt's usefulness is diminishing fast, and falling further behind GPUs. CPUs can't provide large generational performance increases
that GPUs do. The crypto bear market isn't helping.

The mining environement has changed, a multi-algo miner is no longer feasible. Most new coins use their own custom algo now.
Most new miners are also written in C++ and use cmake so they are very difficult to integrate with the cpuminer architecture which is
written all in C and uses autoconf. There is also the bloating issue with trying to support many dissimilar algorithms.

I'm not sure what I'll do or when but it seems the end is in sight.