Just need "depth."
Tweaked strength levels.
Version 5 (Why not?)
Added debugging flags.
This works, but still crashes.
Tweaked flags more.
Possibly fixed bad heap errors.
Some more makefile debuggin flags.
commented out evaler and book.
When skill is disabled, I cannot reproduce heap errors.
I think I fixed it for real this time! It looks like it was the destructor.

I guess that's what "Skill?D()" in the stack traces looked meant.
Cleaning up (hopefully still) working code.
Removed more debugging code.
Match upstream better.
Better skills settings.
Re-added eval and book code to client.
Improvements to engine notes.
Reverted makefile back to normal.
I don't think we need pthread at all.
Merge branch 'async'