Revert removal of compare nesting

Since we want the user to be able to pass a negative comparison function, the extra layer of wrapping is now needed

src/core/matchers/toBeNaN.js

@@ -1,18 +1,20 @@
 getJasmineRequireObj().toBeNaN = function(j$) {
 
   function toBeNaN() {
-    return function(actual) {
-      var result = {
-        pass: (actual !== actual)
-      };
+    return {
+      compare: function(actual) {
+        var result = {
+          pass: (actual !== actual)
+        };
 
-      if (result.pass) {
-        result.message = "Expected actual not to be NaN.";
-      } else {
-        result.message = "Expected " + j$.pp(actual) + " to be NaN.";
+        if (result.pass) {
+          result.message = "Expected actual not to be NaN.";
+        } else {
+          result.message = "Expected " + j$.pp(actual) + " to be NaN.";
+        }
+
+        return result;
       }
-
-      return result;
     };
   }