Cppinize keycache a bit more
* src/keycache.cpp (setSmimeKeySecret, setSmimeKey, setPgpKey), (setPgpKeySecret): Use std::string. (do_locate, locate_secret): Smart pointer for ctx. std::string for addr. * src/keycache.h: Update accordingly.
This avoids free / delete errors and here also reduces
std::string allocations.