make passive-ftp the default

--- a/doc/sample.wgetrc
+++ b/doc/sample.wgetrc
@@ -43,6 +43,7 @@
 # problems supporting passive transfer.  If you are in such
 # environment, use "passive_ftp = off" to revert to active FTP.
 #passive_ftp = off
+passive_ftp = on
 
 # The "wait" command below makes Wget wait between every connection.
 # If, instead, you want Wget to wait only between retries of failed