mkerr.pl: When writing internal FOOerr.h, pay attention to disablable modules

If a module is disablable (i.e. can be configured with 'no-FOO'), the
resulting header file needs to be guarded with a check of the
corresponding OPENSSL_NO_FOO.  While this seem fairly innocuous, it
has an impact on the information in util/*.num, generated by mkdef.pl.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5275)