[gnome-boxes] help: Add note about spice-vdagent

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit c7278de7b4741858b218dc727e66958c221a2771
Author: Federico Bruni <fede inventati org>
Date:   Mon Sep 21 23:11:56 2015 +0200

    help: Add note about spice-vdagent
    
    Add a note about the need to install spice-vdagent in the guest for
    shared clipboard to work, in case of non-express installation.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=755300

 help/C/clipboard.page |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/help/C/clipboard.page b/help/C/clipboard.page
index 899505e..980f53d 100644
--- a/help/C/clipboard.page
+++ b/help/C/clipboard.page
@@ -31,4 +31,16 @@
     <item><p>Switch <gui>Share clipboard</gui> to <gui>ON</gui>.</p></item>
   </steps>
 
+  <note style="important">
+    <p>While express installation typically takes care of making shared
+    clipboard available to you, express installation is not available for all
+    operating systems. In such cases or if you choose manual installation,
+    for shared clipboard to work the SPICE vdagent needs to be installed
+    in the guest. In most Linux-based operating systems the package is
+    called <em>spice-vdagent</em>. If the guest is running a different
+    operating system, check out the
+    <link href="http://www.spice-space.org/download.html";>SPICE download page</link>.
+    </p>
+  </note>
+
 </page>