Transfer: Changed transfer program file extension from .tr to .tra to avoid collision with Troff file extension.

transfer/examples/layout.tra

@@ -0,0 +1,9 @@
+x : Apa
+x = let x : T = y 
+     in case y of
+         f -> q
+         _ -> a
+
+f = apa 
+
+g = bepa