Specify that the ExecutionPolicy template parameter is the first formal

template parameter of a parallel algorithm overload.

Fixes n3554/n3554#51

Author: jaredhoberock

algorithms.html

@@ -148,8 +148,8 @@ <h1><code>ExecutionPolicy</code> algorithm overloads</h1>
       <p>
         Parallel algorithms coexist alongside their sequential counterparts as overloads
         distinguished by a formal template parameter named <code>ExecutionPolicy</code>. This
-        template parameter corresponds to the parallel algorithm's first function parameter, whose
-        type is <code>ExecutionPolicy&amp;&amp;</code>.
+        is the first template parameter and corresponds to the parallel algorithm's first function
+        parameter, whose type is <code>ExecutionPolicy&amp;&amp;</code>.
       </p>
 
       <p>