core: Allow specifying an expiration date for key signatures
* src/context.h (struct gpgme_context): Add 'cert_expire'. * src/engine-gpg.c (append_args_from_cert_expire): New. (gpg_edit): Set option according to the new flag. * src/gpgme.c (gpgme_release): Free 'cert_expire'. (gpgme_set_ctx_flag, gpgme_get_ctx_flag): Add "cert-expire". * tests/gpg/Makefile.am (c_tests): Add new test. (gpg.conf): Write "allow-weak-key-signatures" to gpg.conf. * tests/gpg/t-edit-sign.c: New.
The new context flag "cert-expire" allows setting the expiration date
for key signatures created with gpgme_op_interact.