man: add blurb about using -x with -m if there is no X11 context

src/doc/man/recollindex.1

@@ -109,7 +109,8 @@ Option
 .B
 \-x
 disables this X11 session monitoring (daemon will stay alive even if it
-cannot connect to the X11 server).
+cannot connect to the X11 server). You need to use this too if you use the
+daemon without an X11 context.
 .PP
 .B recollindex \-l 
 will list the names of available language stemmers.

src/doc/user/usermanual.sgml

@@ -651,6 +651,10 @@ fvwm
       <para>There is a similar mechanism under Gnome (find the session
       control tool in the menus and use the "Startup programs" tab).</para>
 
+      <para>If you use the daemon completely out of an X11 session, you
+      need to add option <literal>-x</literal> to disable  X11 session
+      monitoring (else the daemon will not start).</para>
+
       <para>By default, the messages from the indexing daemon will be
         discarded. You may want to change this by setting the
         <literal>daemlogfilename</literal> and