agent: New option --pinentry-invisible-char.
* agent/gpg-agent.c (oPinentryInvisibleChar): New. (opts): Add option. (parse_rereadable_options): Set option. * agent/agent.h (opt): Add field pinentry_invisible_char. * agent/call-pinentry.c (start_pinentry): Pass option to pinentry.
- Signed-off-by: Werner Koch <wk@gnupg.org>