agent: Improve concurrency when Libgcrypt 1.8 is used.
* agent/gpg-agent.c (thread_init_once): Tell Libgcrypt to reinit the system call clamp. (agent_libgcrypt_progress_cb): Do not sleep if Libgcrypt is recent enough.
This patch prepares for a feature comming with Libgcrypt 1.8.
- Signed-off-by: Werner Koch <wk@gnupg.org>