posts.rb: vote on behalf of correct user when moving favorites.

Bug: when an approver moves the favorites of a post, each favorite is
removed from the child post and added to the parent post. For gold+
users, this triggers an upvote, but these upvotes were performed by the
approver rather than the favoriter.

app/models/user.rb

@@ -77,6 +77,7 @@ class User < ActiveRecord::Base
   #after_create :notify_sock_puppets
   has_many :feedback, :class_name => "UserFeedback", :dependent => :destroy
   has_many :posts, :foreign_key => "uploader_id"
+  has_many :post_votes
   has_many :bans, lambda {order("bans.id desc")}
   has_one :recent_ban, lambda {order("bans.id desc")}, :class_name => "Ban"
   has_one :api_key