Add public accessible PublicKeyData/PublicKeyScanner classes
Reduce amount of gpg calls when importing/exporting keys.
Fix rpmdb key import/export (bnc#828672)
No rpmdb key import in readony mode (bnc#828672)
old gcc: define nullptr
old gcc: no explicit operator bool
old gcc: no local type in template
changes 9.16.0 (8)
old gpg2: no --with-sig-list option