Remove windows-1252 encoding.

 -- fails on strings like u'H\ufffdkonsen',
    despite POST['charset'] being 'windows-1252'
Try to keep the POST data intact; previous changeset produces INVALID
non-deprecated urlopen plus additional debugging output for PayPal IPN
handle ValueErrors in PayPal
Ensure PayPal IPN handler doens't return 200 unless all is well.
IPN request encoding workarounds
Fix 100% per-item discounts via PayPal
Merge remote-tracking branch 'DrMeers/master' into next

* DrMeers/master:
  Fix 100% per-item discounts via PayPal
  IPN request encoding workarounds
  Ensure PayPal IPN handler doens't return 200 unless all is well.
  handle ValueErrors in PayPal
  non-deprecated urlopen plus additional debugging output for PayPal IPN
  Try to keep the POST data intact; previous changeset produces INVALID
  Remove windows-1252 encoding.