This commit adds the "--escape-non-printable" option to the repl command.
When specified the REPL console will escape non-printable characters,
printing them as their hex value in square brackets.
This escaping behaviour was previously the default and only behaviour, but
it is now opt-in.
As part of this change, the speed of echoing device data to the console is
improved by by reading and writing in chunks.
Signed-off-by: Damien George <damien@micropython.org>
2771b20d29