Add release notes for parallel compilation driver.

Signed-off-by: Austin Seipp <austin@well-typed.com>

docs/users_guide/7.8.1-notes.xml

@@ -175,6 +175,22 @@
                 declared in the module.
            </para>
        </listitem>
+
+        <listitem>
+            <para>
+                GHC now has a parallel compilataion driver. When
+                compiling with <literal>--make</literal> (which is on
+                by default,) you may also specify
+                <literal>-jN</literal> in order to compile
+                <replaceable>N</replaceable> modules in parallel.
+           </para>
+
+            <para>
+                Note that if you wish for GHC to use multiple cores,
+                you will need to use the <literal>+RTS -N</literal>
+                flag.
+           </para>
+       </listitem>
    </itemizedlist>
   </sect2>
 

docs/users_guide/flags.xml

@@ -2983,6 +2983,12 @@
           </row>
         </thead>
         <tbody>
+          <row>
+            <entry><option>-j <replaceable>N</replaceable></option></entry>
+            <entry>When compiling with <literal>--make</literal>, compile <replaceable>N</replaceable></entry>
+            <entry>dynamic</entry>
+            <entry>-</entry>
+          </row>
           <row>
             <entry><option>-fno-hi-version-check</option></entry>
             <entry>Don't complain about <literal>.hi</literal> file mismatches</entry>

docs/users_guide/using.xml

@@ -596,6 +596,11 @@ ghc Main.hs
           invoked, so the dependencies never get out of sync with the
           source.</para>
         </listitem>
+        <listitem>
+          <para>Using the <literal>-j</literal> flag, you can compile
+          modules in parallel. Specify <literal>-jN</literal> to
+          compile <replaceable>N</replaceable> jobs in parallel.</para>
+        </listitem>
       </itemizedlist>
 
       <para>Any of the command-line options described in the rest of