proxy.config.http.errors.log_error_pages is undocumented

The records.config setting
proxy.config.http.errors.log_error_pages
is undocumented.

Think that this puts any 403/404 etc errors into the error.log file (in addition to the normal access logs).

proxy/http/HttpTransact.cc: if (s->http_config_param->errors_log_error_pages && status_code >= HTTP_STATUS_BAD_REQUEST) {

• its in INT
• think the default is 1 (eg, true)
• setting to 0 stops the bad requests from showing in error.log
• Seems to be reloadable