[doc] INSTALL: details on libclaw with OpenWrt

INSTALL.t2t

@@ -165,10 +165,17 @@ In the configuration (``make menuconfig``), you have to:
 
 + Select the components needed to build (press the <space> key to have a
   //M// or a //*//). For example:
-  - in the //Libraries// menu, select //boost-program_options//,
-    //confuse// and //libiw//;
-  - in the //Base system// menu, //libpthread//, //librt// and
-    //libstdcpp// should now be automatically selected.
+  - in the //Libraries// menu, select //confuse// and //libiw//;
+  - in the //Base system// menu, //libpthread// and //librt// should now
+    be automatically selected (the latter is only needed for OwlPS
+    Positioner).
+
+
+Note that at the moment, //libclaw_tween// is not provided by the
+OpenWrt Buildroot, so if you want to compile OwlPS Positioner you will
+need to add it yourself. You will also need to select
+//boost-program_options// from the //Libraries// menu, then make sure
+//libstdcpp// is selected in the //Base system// menu.
 
 
 == OpenWrt-specific CMake options ==