librustc: Convert all uses of assert over to fail_unless!

src/test/run-pass/trait-inheritance-overloading-simple.rs

@@ -29,7 +29,7 @@ pure fn mi(v: int) -> MyInt { MyInt { val: v } }
 
 pub fn main() {
     let (x, y, z) = (mi(3), mi(5), mi(3));
-    assert x != y;
-    assert x == z;
+    fail_unless!(x != y);
+    fail_unless!(x == z);
 }