add line and file info to 'Malformed line' error msg on *.num files in make-doc-nits
add line and file info to 'Malformed line' error msg on *.num files in make-doc-nits

Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11092)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl