Pidgin 2.5.7

* Yahoo Protocol 16 support, including new HTTPS login method; this should fix a number of login problems that have recently cropped up. (Sulabh Mahajan, Mike "Maiku" Ruprecht)
* Only display the AIM "Unable to Retrieve Buddy List" message once per connection. (Rob Taft)
* Blocking MSN users not on your buddy list no longer disconnects you.
* When performing operations on MSN, assume users are on the MSN/Passport network if we don't get network ID's for them.