* src/gpg-error.def.in (gpgrt_spawn_actions_set_envchange): New.
* src/gpg-error.vers (gpgrt_spawn_actions_set_envchange): New.
* src/gpg-error.h.in (gpgrt_spawn_actions_set_envchange): New.
* src/gpgrt-int.h (_gpgrt_spawn_actions_set_envchange): New.
* src/spawn-posix.c (struct gpgrt_spawn_actions): New field ENVCHANGE.
(prepare_environ): New.
(my_exec): Take care of ENVCHANGE.
(_gpgrt_spawn_actions_set_envchange): New.
* src/spawn-w32.c (struct gpgrt_spawn_actions): New field ENVCHANGE.
(prepare_env_block): New.
(_gpgrt_spawn_actions_set_envchange): New.
(spawn_detached, _gpgrt_process_spawn): Take care of ENVCHANGE.
* src/visibility.c (gpgrt_spawn_actions_set_envchange): New.
* src/visibility.h (gpgrt_spawn_actions_set_envchange): New.
* tests/Makefile.am (TESTS): Add t-spawn.
* tests/t-spawn.c: New.