gpgsm: Use a cache for ISTRUSTED queries.
* sm/call-agent.c (struct istrusted_cache_s): New. (istrusted_cache, istrusted_cache_valid): New. (istrusted_cache_disabled): New. (flush_istrusted_cache): New. (struct istrusted_status_parm_s): New. (istrusted_status_cb): Fill the cache. (gpgsm_agent_istrusted): Implement a cache.
Not a really measurable performance improvements on Linux but maybe
somewhat on Windows (not yet tested). However, it does not clutter
the log files with IPC calls returning NOT_TRUSTED.
- GnuPG-bug-id: T7308