• doc/gpgme.texi: Document it.
• src/engine-assuan.c, src/engine-g13.c, src/engine-gpgconf.c, src/engine-gpgsm.c (_gpgme_engine_ops_): Initialize setexpire to NULL.
• src/engine-gpg.c (gpg_setexpire): New. The implementation. (_gpgme_engine_ops_gpg): Add setexpire.
• src/engine.c (_gpgme_engine_op_setexpire): New. Wrap engine call.
• src/engine.h: (_gpgme_engine_op_setexpire): Add prototype.
• src/genkey.c (set_expire): New. (gpgme_op_set_expire_start, gpgme_op_set_expire): Call set_expire.
• src/gpgme.def, src/gpgme.vers (gpgme_op_set_expire, gpgme_op_set_expire_start): Export it.
• src/gpgme.h.in: Add prototype.
• tests/run-genkey.c: Add set-expire.
  
  -- This extends GPGME to support the --quick-set-expire command added by GnuPG 2.1.22. This allows changing subkeys expiry date without going through the editinteractor interface.
  
  GnuPG-Bug-Id: T4999

Tested with run-generate autotest will follow in qt.