gpg: Refactor the printing of binary notations.
* g10/build-packet.c (sig_to_notation): Break printing of binary notations into... (notation_value_to_human_readable_string): ... this new function. Provide a small preview of the binary data substituting non-printable characters with '?'.
- Signed-off-by: Neal H. Walfield <neal@g10code.com>