Doc nits: callback function typedefs

Doc nits: callback function typedefs

Enhance find-doc-nits to be better about finding typedefs for
callback functions.  Fix all nits it now finds.  Added some new
typedef names to ssl.h some of which were documented but did not
exist

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2151)
(cherry picked from commit 121677b4875b08df99a48d20ab5c26f54782f21d)