sexp: String with \0 is considered "binary".
* src/sexp.c (suitable_encoding): It's "binary" when the buffer contains '\0'.
Backport of master commits of:
5e5dff0551fcd9a826db18188fa1e4a6ca45099a
ddd41eb6ace02626b0bf7704fdec9b765fb717c4
- GnuPG-bug-id: T6747
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>