Fix a number of tests that incorrectly used assertUnreachable.

test/mjsunit/regress/regress-1327557.js

Index: test/mjsunit/regress/regress-1327557.js
diff --git a/test/mjsunit/regress/regress-1327557.js b/test/mjsunit/regress/regress-1327557.js
index bdf4277cca021591369540fa11ddc2991d557bcf..cd8f08f5a7258d0e0632470e5c7e534d912767fb 100644
--- a/test/mjsunit/regress/regress-1327557.js
+++ b/test/mjsunit/regress/regress-1327557.js
@@ -28,9 +28,11 @@
 var x = { valueOf: function() { throw "x"; } };
 var y = { valueOf: function() { throw "y"; } };
 
+var exception = false;
 try {
   x * -y;
-  assertUnreachable("Didn't throw an exception");
 } catch (e) {
+  exception = true;
   assertEquals("y", e);
 }
+assertTrue(exception);