Enhancements to help avoid problems in the CLI when trying display content

Enhancements to help avoid problems in the CLI when trying display content
that contains ANSI escape codes:  (1) Add the --escape MODE option to the CLI
where MODE is one of "symbol", "ascii", "off" where the default is "symbol".
(2) Add the unistr() SQL function.  (3) Add the unistr_quote() SQL function.
(4) Add the %#Q and %#q conversions in the built-in printf.

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