jQuery.prev: Clarified its behavior

Fixes gh-861
Closes gh-873

entries/prev.xml

@@ -7,7 +7,7 @@
       <desc>A string containing a selector expression to match elements against.</desc>
     </argument>
   </signature>
-  <desc>Get the immediately preceding sibling of each element in the set of matched elements, optionally filtered by a selector.</desc>
+  <desc>Get the immediately preceding sibling of each element in the set of matched elements. If a selector is provided, it retrieves the previous sibling only if it matches that selector.</desc>
   <longdesc>
     <p>Given a jQuery object that represents a set of DOM elements, the <code>.prev()</code> method searches for the predecessor of each of these elements in the DOM tree and constructs a new jQuery object from the matching elements.</p>
     <p>The method optionally accepts a selector expression of the same type that can be passed to the <code>$()</code> function. If the selector is supplied, the preceding element will be filtered by testing whether it match the selector.</p>