MWL#55 : force per-machine installation.

Problem: user without privileges can have an half-complete
installation, if he manages to click on "Ignore" for all  errors
in the installer. 

As a result, he will miss ARP registry keys, and uninstall 
will not be possible using  "Add/Remove Programs" applet.

win/packaging/extra.wxs.in

@@ -28,7 +28,8 @@
     <Property Id="DEFAULTUSER" Secure="yes"/>
     <!-- Whether to data on uninstall (default yes, after asking user consent) -->
     <Property Id="CLEANUPDATA" Secure="yes" Value="1"/>
-
+    <!-- Force per machine installation -->
+    <Property Id="ALLUSERS" Secure="yes" Value="1"/>
 
     <!-- 
       User interface dialogs 
@@ -638,5 +639,9 @@
       >
       NOT NSISINSTALLKEY OR Installed
     </Condition>
+    <Condition Message=
+       'Setting the ALLUSERS property is not allowed because [ProductName] is a per-machine application. Setup will now exit.'>
+      <![CDATA[ALLUSERS = "1"]]>
+    </Condition>
   </Fragment>
 </Wix>