removed unused/non-portable with_tmp_fifo;

--- a/src/Pure/System/isabelle_system.ML	Sun Jan 11 20:40:14 2015 +0100
+++ b/src/Pure/System/isabelle_system.ML	Sun Jan 11 20:45:03 2015 +0100
@@ -15,7 +15,6 @@
   val create_tmp_path: string -> string -> Path.T
   val with_tmp_file: string -> string -> (Path.T -> 'a) -> 'a
   val with_tmp_dir: string -> (Path.T -> 'a) -> 'a
-  val with_tmp_fifo: (Path.T -> 'a) -> 'a
   val bash_output: string -> string * int
   val bash: string -> int
 end;
@@ -114,15 +113,5 @@
     val _ = mkdirs path;
   in Exn.release (Exn.capture f path before ignore (try rm_tree path)) end;
 
-
-(* fifo *)
-
-fun with_tmp_fifo f =
-  with_tmp_file "isabelle-fifo-" ""
-    (fn path =>
-      (case bash_output ("mkfifo -m 600 " ^ File.shell_path path) of
-        (_, 0) => f path
-      | (out, _) => error (trim_line out)));
-
 end;