fuseDistribution: add rotation in usage message

Examples/fuseDistributions.cpp

@@ -48,6 +48,9 @@ void usage(const std::string& progname) {
         "        Duplicate the distribution inside a grid of gx by gy by gz dimensions.\n"
         "        gx, gy and gz are integers. The grid center is governed by the -c \n"
         "        option.\n"
+        "      -r rx:ry:rz\n"
+        "        Rotate the distribution around its x, y and z axes. The rotation \n"
+        "        center is the distribution center. rx, ry and rz are in radians.\n"
         "\n"
         "  --extra-length length\n"
         "    Length to be added to the final box width.\n"