error string handling for OpenSSL-3.0.0 needs further fixing

[msalle]

My comment from original "OpenSSL-3.0.0-beta1 fixes" merge request:

I just realised that for a proper fix for OpenSSL3.0 all occurrences of ERR_PACK need to be checked, since the function part is deprecated and set to 0 in ERR_PACK. That can result in overwriting other entries (library name or reasons).
This concerns:

• src/ac/error.c: should be skipped entirely
• src/sslutils/scutils.c: should skip loading the scerr_str_functs
• src/sslutils/sslutils.c: should skip loading the prxyerr_str_functs
  Also references to ERR_func_error_string also need adapting since that will always be (null). That concerns src/socklib/Server.cpp and src/common/data.cc
  All these are not really breaking voms, but can lead to misleading and/or faulty error messages.
  See also Remove func name from errors, etc. openssl/openssl#9058

Originally posted by @msalle in #98 (comment)

[giacomini]

@msalle would you please have a look at the changes in #133? it's quite minimal and doesn't cover all what is needed for properly handling errors according to OpenSSL 3, but at least it should allow to have correctly formatted error messages. Thanks.

[giacomini]

I have merged the PR with the existing changes. I'll address the rest of this issue subsequently.