before(): Document new callback signature

Since jQuery version 1.10, `$.fn.before` invokes the supplied function
with two arguments: the numeric index of each element in the set and the
string markup describing each element's contents. Remove the second
argument from the documentation of the pre-1.10 signature and add a new
entry to thoroughly document the post-1.10 signature.

Author: jugglinmike

entries/before.xml

@@ -22,7 +22,6 @@
     <added>1.4</added>
     <argument name="function" type="Function">
       <argument name="index" type="Integer" />
-      <argument name="html" type="String" />
       <return>
         <type name="htmlString"/>
         <type name="Element"/>
@@ -31,6 +30,20 @@
       <desc>A function that returns an HTML string, DOM element(s), or jQuery object to insert before each element in the set of matched elements. Receives the index position of the element in the set as an argument. Within the function, <code>this</code> refers to the current element in the set.
       </desc>
     </argument>
+  </signature>
+   <signature>
+    <added>1.10</added>
+    <argument name="function" type="Function">
+      <argument name="index" type="Integer" />
+      <argument name="html" type="String" />
+      <return>
+        <type name="htmlString"/>
+        <type name="Element"/>
+        <type name="jQuery"/>
+      </return>
+      <desc>A function that returns an HTML string, DOM element(s), or jQuery object to insert before each element in the set of matched elements. Receives the index position of the element in the set and the old HTML value of the element as arguments. Within the function, <code>this</code> refers to the current element in the set.
+      </desc>
+    </argument>
   </signature>
   <desc>Insert content, specified by the parameter, before each element in the set of matched elements.</desc>
   <longdesc>