Fix use cases of snprintf.
* agent/call-pinentry.c, agent/call-scd.c, agent/command.c, build-aux/speedo/w32/g4wihelp.c, common/get-passphrase.c, dirmngr/dirmngr.c, g10/call-agent.c, g10/cpr.c, g10/keygen.c, g10/openfile.c, g10/passphrase.c, scd/app-openpgp.c, scd/scdaemon.c, sm/call-agent.c, sm/call-dirmngr.c, sm/certreqgen.c: Fix assuming C99.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>