These produce the binary representation of a number.
'%#b' and '%#B' prefix with '0b' and '0B', respectively.
(bug#79990)
* etc/NEWS: Announce change.
* doc/lispref/strings.texi (Formatting Strings): Describe new format
specs and add to comment on reconstructing the value with 'read'.
* src/editfns.c (format): Update doc string.
(styled_format): Add support for '%b' and '%B'. To remain
portable, avoid use of 'sprintf' by converting by hand.
* test/src/editfns-tests.el (format-binary-zero, format-binary-floats)
(format-binary-nonzero-integers): Add tests.
(read-large-integer): Add binary test cases.
Co-authored-by: Paul Eggert <eggert@cs.ucla.edu>
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