Make rst/md presence more amenable to help2man

Both start & stop ANSI SGR sequences can be included in all the emitted help. This can make it easier to automate translation to troff for man page contexts. Also add a few new osUt utility APIs.

Default enum parsing bug fix

Fix bug in cligen/argcvt parsing enums where one could not prefix another (e.g. blue & bluegreen could not be in the same enum set).

Get rid of various warnings

As Nim-1.6 approaches, tweak code to no longer generate warnings for the library itself or for example programs. Might be one or two not very hot code paths lingering.

Config file fixin's

Better support CLuser-written config files via both cligen-included cligen/clCfg(Init|Toml) and CLauthor included cligen/mergeCfgEnv checking decls before import to block compiler issued duplicate import warnings.

Also, update cligen/clCfg(Init|Toml) to find a simple ~/.config/cligen file as opposed to only finding ~/.config/cligen/ directories. (Might be helpfully simpler for conscientious objectors to LC_THEME complexity.)

Fix several warnings; Add getTmNs, dtNS

Get most warnings suppressed in preparation for hopefully soon Nim-1.6.0. (TaintedString deprecations will probably warn until removed and then just go away since I try to support back to Nim-0.19.2).

Also add some very easy to use time queries in cligen/posixUt and warn if int is not 64-bits.

A few minor fixes & new API calls

Mostly procpool.noop to ease life when there is no result to write back and then inside osUt we grew popenr, popenw & pclose and also mkdirTo & mkdirOpen, and replacingUrite (for nio/lp2term) and finally an ARM64 portability thing for cligen/magic. (A few doc clean-ups, too.)

Various tune-ups & additions

See release notes for details. This bump is mostly to use as a dependency for an inbound new package.

Customization of what to do with SIGPIPE

This is a better resolution of/adaption to the new Nim stdlib SIGPIPE behavior.

Also some minor tweaks. See RELEASE_NOTES.md for details.

Cleaner fix for Nim CI

Also, add osUt.seekable and fix urite to raise for hldiff.

procpool tweaking & Nim CI fix

RELEASE_NOTES.md has details/links to more.