cpan.js: un-break Shift+Enter -> IFL feature

I broke the Shift+Enter IFL feature while solving a bug in
140605c.

Now we can:

 * Shift+Enter to do IFL
 * Click the IFL button

*Without* implicitly adding a "1" to search queries and thus throwing
them off.

I've only tested this in Chrome but it's using some pretty basic W3C
core API to append the element, so it probably shouldn't break
anywhere.

root/static/js/cpan.js

@@ -88,7 +88,16 @@ $(document).ready(function() {
     $('#search-input').keydown(function(event) {
         if (event.keyCode == '13' && event.shiftKey) {
             event.preventDefault();
-            document.forms[0].q.name = 'lucky';
+
+            /* To make this a lucky search we have to create a new
+             * <input> element to pass along lucky=1.
+             */
+            var luckyField = document.createElement("input");
+            luckyField.type = 'hidden';
+            luckyField.name = 'lucky';
+            luckyField.value = '1';
+            document.forms[0].appendChild(luckyField);
+
             document.forms[0].submit();
         }
     });
@@ -222,4 +231,4 @@ function favDistribution(form) {
         }
     });
     return false;
-}
+}