Mention that generalised list comprehensions are enabled with -XTransformListComp

docs/users_guide/flags.xml

@@ -856,7 +856,7 @@
 	    </row>
 	    <row>
 	      <entry><option>-XTransformListComp</option></entry>
-	      <entry>Enable <link linkend="generalised-list-comprehensions">transform list comprehensions</link>.</entry>
+	      <entry>Enable <link linkend="generalised-list-comprehensions">generalised list comprehensions</link>.</entry>
 	      <entry>dynamic</entry>
 	      <entry><option>-XNoTransformListComp</option></entry>
 	    </row>

docs/users_guide/glasgow_exts.xml

@@ -1008,6 +1008,7 @@ This name is not supported by GHC.
 	paper <ulink url="http://research.microsoft.com/~simonpj/papers/list-comp">
 	  Comprehensive comprehensions: comprehensions with "order by" and "group by"</ulink>,
     except that the syntax we use differs slightly from the paper.</para>
+<para>The extension is enabled with the flag <option>-XTransformListComp</option>.</para>
 <para>Here is an example: 
 <programlisting>
 employees = [ ("Simon", "MS", 80)