added mkdir;

--- a/src/Pure/General/file.ML	Tue Mar 09 12:09:05 1999 +0100
+++ b/src/Pure/General/file.ML	Tue Mar 09 12:09:22 1999 +0100
@@ -22,6 +22,7 @@
   eqtype info
   val info: Path.T -> info option
   val exists: Path.T -> bool
+  val mkdir: Path.T -> unit
 end;
 
 structure File: FILE =
@@ -87,4 +88,9 @@
 val exists = is_some o info;
 
 
+(* mkdir *)
+
+fun mkdir path = (execute ("mkdir -p " ^ enclose "'" "'" (sysify path)); ());
+
+
 end;