better debugging for d3 prototype

[monkyyy]

https://github.com/crazymonkyyy/debuglibprototype

in response to this thread, adr suggest opend may change -J to 
`.` by default: 
https://forum.dlang.org/thread/ejkrtibofyeyadrzxgkg@forum.dlang.org

This enables better "unmixing", as I think this enables better 
print-debuging api, so I made a prototype and will probaly be 
trying to make something nice for open d

run `dmd -i -J=. -main -run test.d 0`, try changing the loglevel

discuss