CURLOPT_PINNEDPUBLICKEY.3: added details

docs/libcurl/opts/CURLOPT_PINNEDPUBLICKEY.3

@@ -32,20 +32,34 @@ Pass a pointer to a zero terminated string as parameter. The string should be
 the file name of your pinned public key. The format expected is "DER".
 
 When negotiating a TLS or SSL connection, the server sends a certificate
-indicating its identity. A public key is extracted from this certificate
-and if it does not exactly match the public key provided to this option,
-curl will abort the connection before sending or receiving any data.
-
-This is currently only implemented in the OpenSSL backend, with more backends
-expected to follow shortly.
+indicating its identity. A public key is extracted from this certificate and
+if it does not exactly match the public key provided to this option, curl will
+abort the connection before sending or receiving any data.
 .SH DEFAULT
 NULL
 .SH PROTOCOLS
 All TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
 .SH EXAMPLE
-TODO
+.nf
+CURL *curl = curl_easy_init();
+if(curl) {
+  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+  curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, "/etc/publickey.der");
+
+  /* Perform the request */
+  curl_easy_perform(curl);
+}
+.fi
 .SH AVAILABILITY
-If built TLS enabled.
+If built TLS enabled. This is currently only implemented in the OpenSSL,
+GnuTLS and GSKit backends.
+
+Added in libcurl 7.39.0
 .SH RETURN VALUE
 Returns CURLE_OK if TLS enabled, CURLE_UNKNOWN_OPTION if not, or
 CURLE_OUT_OF_MEMORY if there was insufficient heap space.
+.SH "SEE ALSO"
+.BR CURLOPT_SSL_VERIFYPEER "(3), "
+.BR CURLOPT_SSL_VERIFYHOST "(3), "
+.BR CURLOPT_CAINFO "(3), "
+.BR CURLOPT_CAPATH "(3), "