revert renaming "sender" to "from" to maintain backwards compatibility

api.lua

@@ -67,7 +67,7 @@ function mail.send(src, dst, subject, body)
 	-- form the actual mail
 	local msg = {
 		unread  = true,
-		from    = m.from,
+		sender  = m.from,
 		to      = m.to,
 		subject = m.subject,
 		body    = m.body,

gui.lua

@@ -60,7 +60,7 @@ function mail.show_inbox(name)
 				end
 			end
 			formspec[#formspec + 1] = ","
-			formspec[#formspec + 1] = minetest.formspec_escape(message.from)
+			formspec[#formspec + 1] = minetest.formspec_escape(message.sender)
 			formspec[#formspec + 1] = ","
 			if message.subject ~= "" then
 				if string.len(message.subject) > 30 then
@@ -102,7 +102,7 @@ function mail.show_message(name, msgnumber)
 			button[6,8.5;2,1;delete;Delete]
 		]] .. theme
 
-	local from = minetest.formspec_escape(message.from)
+	local from = minetest.formspec_escape(message.sender)
 	local to = minetest.formspec_escape(message.to)
 	local cc = minetest.formspec_escape(message.cc)
 	local subject = minetest.formspec_escape(message.subject)
@@ -144,7 +144,7 @@ end
 function mail.reply(name, message)
 	mail.ensure_new_format(message)
 	local replyfooter = "Type your reply here.\n\n--Original message follows--\n" ..message.body
-	mail.show_compose(name, message.from, "Re: "..message.subject, replyfooter)
+	mail.show_compose(name, message.sender, "Re: "..message.subject, replyfooter)
 end
 
 function mail.replyall(name, message)
@@ -152,8 +152,8 @@ function mail.replyall(name, message)
 	local replyfooter = "Type your reply here.\n\n--Original message follows--\n" ..message.body
 	-- new recipients are the sender plus the original recipients, minus ourselves
 	local recipients = message.to
-	if message.from ~= nil then
-		recipients = message.from .. ", " .. recipients
+	if message.sender ~= nil then
+		recipients = message.sender .. ", " .. recipients
 	end
 	recipients = mail.parse_player_list(recipients)
 	for k,v in pairs(recipients) do

util/normalize.lua

@@ -50,7 +50,6 @@ end
 
 function mail.ensure_new_format(message)
     if message.sender then
-        message.from = message.sender
         message.to = name
     end
 end