UTF-8 improvements

Don't corrupt UTF-8 strings with SAFECOPY() (use new SAFECOPY_UTF8).

Some terminals (notably, Windows Terminal) display zero width UNICODE chars
as a single column-wide space. <sigh> Auto-detect the zero-width "width"
(1 or 0) of the terminal during connection and UTF-8 auto-detection.

getstr() works a lot better now with UTF-8 strings with wide chars (e.g.
emojis), but likely much more to do.