remove attribute hidden for GCC build on windows
remove attribute hidden for GCC build on windows

OSVR/OSVR-Core,OSVR/OSVR-Core,godbyk/OSVR-Core,leemichaelRazer/OSVR-Core,leemichaelRazer/OSVR-Core,leemichaelRazer/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,leemichaelRazer/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,godbyk/OSVR-Core