Cleanup of mjsunit.js code and make assertEquals more strict.

test/mjsunit/regexp-static.js

Index: test/mjsunit/regexp-static.js
diff --git a/test/mjsunit/regexp-static.js b/test/mjsunit/regexp-static.js
index 9e73f3d6ffaa2819cb02a56531c169bb550e17f8..0f849687cc65d0d83d8d1eb0e875e16acfbc11e7 100644
--- a/test/mjsunit/regexp-static.js
+++ b/test/mjsunit/regexp-static.js
@@ -134,7 +134,8 @@ function f() { return RegExp.$1; };
 assertEquals('abcd', 'abcd'.replace(re, f));
 
 // lastParen where the last parenthesis didn't match.
-assertEquals("foo,", /foo(?:a(x))?/.exec("foobx"), "lastParen setup");
+assertEquals(["foo",undefined], /foo(?:a(x))?/.exec("foobx"),
+             "lastParen setup");
 assertEquals("", RegExp.lastParen, "lastParen");
 
 // The same test for $1 to $9.