Add missing false return type in openssl_x509_parse documentation

Author: cedric-anne

reference/openssl/functions/openssl-x509-parse.xml

@@ -52,6 +52,7 @@
   <para>
    <emphasis>The structure of the returned data is (deliberately) not
    yet documented, as it is still subject to change.</emphasis>
+   On failure, &false; is returned.
   </para>
  </refsect1>