fixed tempfile issue on Windows

-import sys, os, os.path
+import sys, os, os.path, tempfile
 import gtk, pango, gobject
 import bones.asm as asm
 import bones.cpu
@@ -580,10 +580,9 @@ class CodeEditor (gtk.VBox) :
                 asm.save(_new_file("Save BIOS as..."))
                 self._set_status("BIOS saved", 1)
             elif resp == gtk.RESPONSE_APPLY :
-                name = os.tmpnam()
-                tmp = open(name, "w")
-                tmp.write(asm.dump())
-                tmp.close()
+                fd, name = tempfile.mkstemp()
+                with os.fdopen(fd, "w") as tmp :
+                    tmp.write(asm.dump())
                 bones.cmd.launch("bones_machine.py", "--tmpfile", name)
                 self._clear_status()
             else :