util/mkdef.pl: Trust configdata.pm

This script kept its own database of disablable algorithms, which is a
maintenance problem, as it's not always perfectly in sync with what
Configure does.  However, we do have all the data in configdata.pm,
produced by Configure, so let's use that instead.

Also, make sure to parse the *err.h header files, as they contain
function declarations that might not be present elsewhere.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5157)