PPCI (Pure Python Compiler Infrastructure) 0.5.8

0.5.8 major changes include:

* Better support of ELF files for easier interoperability with host environment (e.g. while PPCI doesn't support shared libs, those can be linked with host `ld`).

* Many improvements to C frontend.

* Many improvements to WASM support.

* Some improvements to Pascal frontend.

* Improvements to graph-coloring register allocation in the backend.

* Docs (https://ppci.readthedocs.io/) improvements.