cpp: Add interactor to revoke a key
* lang/cpp/src/global.h (enum class RevocationReason): New. * lang/cpp/src/gpgrevokekeyeditinteractor.cpp, lang/cpp/src/gpgrevokekeyeditinteractor.h: New. * lang/cpp/src/Makefile.am: Add new files.
- GnuPG-bug-id: T5904