We don't want ANSI escape-sequences written in tests since it is a pain
to check the output with ut_assert_nextline() et al.
Provide a way to tests to request that these characters not be sent.
Add a proper function comment while we are here, to encourage others.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>