Simplify isMailResolvable and accept keygen
* src/keycache.cpp (isMailResolvable): Return bool. Accept potential keygen. * src/keycache.h: Update accordingly. * src/mail.cpp (Mail::autoresolve_check_s): Update for new API.
This inly check for a self key for SMIME. For OpenPGP we can
generate a key.
- GnuPG-Bug-Id: T3999