+ Additional explanation about Append erros.

docs/ref.tex

@@ -5022,7 +5022,9 @@ Procedure Append (Var F : Text);
 append mode.
 
 \Errors
-If the file doesn't exists, a run-time error will be generated.
+If the file doesn't exist when appending, a run-time error will be generated.
+This behaviour has changed on Windows and Linux platforms, where in versions
+prior to 1.0.6, the file would be created in append mode.
 \SeeAlso
 \seep{Rewrite},\seep{Close}, \seep{Reset}
 \end{procedure}