Make editorial changes suggested by Rich Salz and add the -rsigopt option to...

Make editorial changes suggested by Rich Salz and add the -rsigopt option to the man page for the ocsp command.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4190)