Pervasive changes to console_io.{c,h} in support of simplifying ubiquitous emit ops...

Pervasive changes to console_io.{c,h} in support of simplifying ubiquitous emit ops in shell, and to get better control of console streams that might be opened only via .read or .output commands. Changes to shell to use {s,o,e}put{f,z}(...) calls for initial testing, but this check-in has few such conversions so that most will be in a separate check-in. Many renames to better follow recent coding convention. This code seems to be working, but has not been tested on difficult platforms or with multiple console hosts yet. So it is a WIP.

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