* src/engine-gpg.c (read_status): Remove the handling of
GPGME_STATUS_END_STREAM; this was used only by the former experimental
--pipemode of gpg but that is not even anymore invoked here.
(struct engine_gpg): Remove cmd.linked_data and .linked_idx.
(build_argv): Remove code for linked_data.
(gpg_new): Ditto.
(gpg_set_command_handler): Remove arr linked_data.
* src/engine-backend.h (engine_ops): Remove arg data from
set_command_handler.
* src/engine.c (_gpgme_engine_set_command_handler): Remove arg
linked_data and adjust all callers.