Make some tests less flaky on windows.

Be sure to join() the panicking threads so they're not running when the program
is shutting down.

Author: alexcrichton

src/test/run-pass/unwind-resource.rs

@@ -37,7 +37,7 @@ fn f(tx: Sender<bool>) {
 
 pub fn main() {
     let (tx, rx) = channel();
-    let _t = thread::spawn(move|| f(tx.clone()));
+    let _t = thread::scoped(move|| f(tx.clone()));
     println!("hiiiiiiiii");
     assert!(rx.recv().unwrap());
 }

src/test/run-pass/unwind-unique.rs

@@ -19,5 +19,5 @@ fn f() {
 }
 
 pub fn main() {
-    let _t = thread::spawn(f);
+    let _t = thread::scoped(f);
 }