Space optimization define & a few utility procs

If you don't care about config files and nice generated help colors, but you do care about object file sizes, then look into --define:cgCfgNone and #207 .

BREAKING CHANGE: in the both unlikely and unwise case that you relied upon import cligen/humanUt exporting initHashSet, toHashSet - you can no longer.

Harden cligen/procpool a bit more and add a new examples/piPar.nim that runs 1000s of times faster than similar renditions of this already slow way to compute π (pi).

Also, courtesy of @Vindaar a docCommentAdd for compile-time computed documentation and a few other utility APIs like nextSlice, echoQuit130 proc for setControlCHook, etc. See RELEASE_NOTES.md for more details.