filter unused libwps_tools_win:: methods

Change-Id: I88fca8854db96fdba1ea9069fb95a237c5b02bb2

Makefile

@@ -487,6 +487,7 @@ findunusedcode:
               | grep -v ^libcmis:: \
               | grep -v ^libvisio:: \
               | grep -v ^libwpg:: \
+              | grep -v ^libwps_tools_win:: \
               | grep -v ^lucene:: \
               | grep -v ^Matrix3d:: \
               | grep -v ^salhelper:: \