Loosen possibly bogus constraints in backtrace test

src/test/run-pass/backtrace.rs

@@ -57,7 +57,9 @@ fn runtest(me: &str) {
     let out = p.wait_with_output().unwrap();
     assert!(!out.status.success());
     let s = str::from_utf8(out.error.as_slice()).unwrap();
-    assert!(s.contains("stack backtrace") && s.contains("double::h"),
+    // loosened the following from double::h to double:: due to
+    // spurious failures on mac, 32bit, optimized
+    assert!(s.contains("stack backtrace") && s.contains("double::"),
             "bad output3: {}", s);
 
     // Make sure a stack trace isn't printed too many times