fix the syntax of std::ostringstream for linux build
fix the syntax of std::ostringstream for linux build

d235j/OSVR-Core,d235j/OSVR-Core,feilen/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,leemichaelRazer/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,feilen/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,d235j/OSVR-Core,OSVR/OSVR-Core,d235j/OSVR-Core,feilen/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,godbyk/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,d235j/OSVR-Core