True when Stream is a stream to the opened HTTP log file. Opens the
log file in append mode if the file is not yet open. The log file
is determined from the setting http:logfile. If this setting is
set to the empty atom (''), this predicate fails.
If a file error is encountered, this is reported using
print_message/2, after which this predicate silently fails. Opening
is retried every minute when a new message arrives.
Before opening the log file, the message http_log_open(Term) is
broadcasted. This message allows for creating the directory,
renaming, deleting or truncating an existing log file.
