* src/abstractimportjob.cpp: New.
* src/changeexpiryjob.cpp (ChangeExpiryJob::ChangeExpiryJob,
ChangeExpiryJob::~ChangeExpiryJob): New.
* src/importfromkeyserverjob.cpp: New.
* src/importjob.cpp (ImportJob::ImportJob, ImportJob::~ImportJob): New.
* src/listallkeysjob.cpp (ListAllKeysJob::ListAllKeysJob,
ListAllKeysJob::~ListAllKeysJob): New.
* src/receivekeysjob.cpp: New.
* src/job.cpp: Remove make_job_subclass(_ext) macros for above Job
classes.