core: New global flag "require-gnupg".
* src/gpgme.c (gpgme_set_global_flag): Add flag. * src/engine.c (engine_minimal_version): New variable. (_gpgme_set_engine_minimal_version): New function. (gpgme_get_engine_info): Check that flag. * tests/run-keylist.c (main): New option --require-gnupg.
- Signed-off-by: Werner Koch <wk@gnupg.org>