add docs for OCSP_resp_get0_signature

Reviewed-by: NPaul Dale <paul.dale@oracle.com>
Reviewed-by: NMatthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/7082)

doc/man3/OCSP_resp_find_status.pod

@@ -7,6 +7,7 @@ OCSP_resp_get0_signer,
 OCSP_resp_get0_id,
 OCSP_resp_get1_id,
 OCSP_resp_get0_produced_at,
+OCSP_resp_get0_signature,
 OCSP_resp_get0_tbs_sigalg,
 OCSP_resp_get0_respdata,
 OCSP_resp_find_status, OCSP_resp_count, OCSP_resp_get0, OCSP_resp_find,
@@ -35,6 +36,7 @@ OCSP_basic_verify
  const ASN1_GENERALIZEDTIME *OCSP_resp_get0_produced_at(
                              const OCSP_BASICRESP* single);
 
+ const ASN1_OCTET_STRING *OCSP_resp_get0_signature(const OCSP_BASICRESP *bs);
  const X509_ALGOR *OCSP_resp_get0_tbs_sigalg(const OCSP_BASICRESP *bs);
  const OCSP_RESPDATA *OCSP_resp_get0_respdata(const OCSP_BASICRESP *bs);
  const STACK_OF(X509) *OCSP_resp_get0_certs(const OCSP_BASICRESP *bs);
@@ -86,6 +88,8 @@ B<*revtime>, B<*thisupd> and B<*nextupd>.
 OCSP_resp_get0_produced_at() extracts the B<producedAt> field from the
 single response B<bs>.
 
+OCSP_resp_get0_signature() returns the signature from B<bs>.
+
 OCSP_resp_get0_tbs_sigalg() returns the B<signatureAlgorithm> from B<bs>.
 
 OCSP_resp_get0_respdata() returns the B<tbsResponseData> from B<bs>.