env: Fix reference to syntax.py

env.ps1: Fix domut not working

env.ps1: Add domut_ci command

env.ps1: Get UTF-8 working in PowerShell pipes

env: Run long test with only 4 jobs ...

This will probably break other people's systems, but Hypothesis memory
growth means my system can't even run the long tests without running out
of memory.

env: Tailor dotest for dev purposes ...

dotest now does the following things:

- Passes extra args to pytest
- Exits on first error
- Prince locals on error
- Runs last error test in next invocation

build: Add script to build NewLang.pyz

env.ps1: Us python -m pip to avoid weird bugs ...

The Python.Python.3 package on Windows seems to break if you try to
update pip using the pip command. Maybe because the pip binary is in use
during the upgrade?

env: Add domut for mutmut testing

env.ps1: Prefix commands with 'do' to avoid namespacing

env.ps1: Add Windows environment for development