XFAIL spawnfail and task-comm-15

Author: brson

src/test/run-fail/spawnfail.rs

@@ -1,3 +1,4 @@
+// xfail-test
 // error-pattern:explicit
 use std;
 import std::task;

src/test/run-pass/task-comm-15.rs

@@ -1,3 +1,4 @@
+// xfail-test
 // xfail-win32
 use std;
 import std::comm;