* src/gpgme.h.in (GPGME_PROTOCOL_SPAWN): New.
(GPGME_SPAWN_DETACHED, GPGME_SPAWN_ALLOW_SET_FG): New.
* src/gpgme.c (gpgme_set_protocol): Add new protocol.
(gpgme_get_protocol_name): Ditto.
* src/spawn.c: New.
* src/libgpgme.vers, src/gpgme.def: Add new public functions.
* src/engine-spawn.c: New.
* src/Makefile.am: Add new files.
* src/engine-backend.h (struct engine_ops): Add OPSPAWN.
* src/engine.c (engine_ops): Add _gpgme_engine_ops_spawn.
(gpgme_get_engine_info): Add Spawn to the list of protocols.
(_gpgme_engine_op_spawn): New.
* src/gpgme-tool.c (gt_protocol_from_name): Add new protocol.
(gt_spawn, cmd_spawn): New.