xfailing pipe-detect-term on Windows, because it requires failure.

src/test/run-pass/pipe-detect-term.rs

@@ -1,6 +1,7 @@
 // Make sure that we can detect when one end of the pipe is closed.
 
 // xfail-pretty
+// xfail-win32
 
 use std;
 import std::timer::sleep;