ftpserver: output CRLF in logs

Previously the log function would just filter out all CR and LF
occurances from the log to make it more readable. This had the downside
that it made it very hard to see CR LFs when they actually matters.

Now, they're instead converted to "[CR]" and "[LR]" in the log to become
apparent to readers.

tests/ftpserver.pl

@@ -327,7 +327,8 @@ sub sendcontrol {
     my $log;
     foreach $log (@_) {
         my $l = $log;
-        $l =~ s/[\r\n]//g;
+        $l =~ s/\r/[CR]/g;
+        $l =~ s/\n/[LF]/g;
         logmsg "> \"$l\"\n";
     }
 }