rm fifo after open;

--- a/src/Pure/Tools/isabelle_process.ML	Thu Aug 28 19:31:55 2008 +0200
+++ b/src/Pure/Tools/isabelle_process.ML	Thu Aug 28 19:34:51 2008 +0200
@@ -103,7 +103,7 @@
     if out = "" orelse out = "-" then TextIO.stdOut
     else
       let val path = File.platform_path (Path.explode out)
-      in TextIO.openOut path (* before OS.FileSys.remove path *) end;
+      in TextIO.openOut path before OS.FileSys.remove path end;
   in
     Output.writeln_fn  := message out_stream "A" Markup.writelnN;
     Output.priority_fn := message out_stream "B" Markup.priorityN;