parameter.
If B<PKCS7_REUSE_DIGEST> is set then an attempt is made to copy the content
-digest value from the PKCS7 struture: to add a signer to an existing structure.
+digest value from the PKCS7 structure: to add a signer to an existing structure.
An error occurs if a matching digest value cannot be found to copy. The
returned PKCS7 structure will be valid and finalized when this flag is set.