documentation/poky-ref-manual/ref-features.xml: YOCTO #1104 EXTRA_IMAGE_FEATURES

The Images reference section states you can control what features are
in an image by using the IMAGE_FEATURES variable.  It failed to mention
the EXTRA_IMAGE_FEATURES variable.  I included this variable in the
discussion.

(From yocto-docs rev: 0149133ce08e161cffc2a66721537a17623da79e)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/poky-ref-manual/ref-features.xml

@@ -211,12 +211,14 @@
         <title>Reference: Images</title>
 
         <para>
-            The contents of images generated by Poky can be controlled by the <glossterm
-        linkend='var-IMAGE_FEATURES'><link
-        linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>
-        variable in local.conf. Through this you can add several different
-        predefined packages such as development utilities or packages with debug
-        information needed to investigate application problems or profile applications.
+            The contents of images generated by Poky can be controlled by the 
+            <glossterm linkend='var-IMAGE_FEATURES'><link linkend='var-IMAGE_FEATURES'>
+            IMAGE_FEATURES</link></glossterm> variable and the in local.conf and the 
+            <glossterm linkend='var-EXTRA_IMAGE_FEATURES'><link linkend='var-EXTRA_IMAGE_FEATURES'>
+            EXTRA_IMAGE_FEATURES</link></glossterm> that you typically configure in your image recipes.
+            Through these varibales you can add several different
+            predefined packages such as development utilities or packages with debug
+            information needed to investigate application problems or profile applications.
         </para>
 
         <para>