recent prog8 version creates better code, also linkedlist benchmark was added

Hello,
I've just released prog8 6.4
It contains once again various code generation improvements. (mostly added in 6.1)
Most notably, the plasma benchmark now runs faster than the optimized cc65 one.
Also i've added the linkedlist benchmark that was missing until now.

It would be awesome, if you could update the graphs with the new results?
(it does first require some slight changes in the prog8 benchmark programs because of the changes to the language and libraries. The pull request for that is linked below.)

I've now pretty much exhausted the possibilities of easy to moderately complex code generation optimizations in Prog8. Further improvements will require quite a lot of work, I think, something I don't have the time for any time soon.

Locate the benchmark programs and graph-generation workflow in this repository; the issue names no files or runnable entry point. Review the referenced Prog8 benchmark changes, include the new linkedlist benchmark and updated results, and verify that the graphs reflect them.

Written by the indexing model from the issue text.