do predef of __cplusplus so that things like default arguments show in docs.
do predef of __cplusplus so that things like default arguments show in docs.

leemichaelRazer/OSVR-Core,Armada651/OSVR-Core,godbyk/OSVR-Core,leemichaelRazer/OSVR-Core,d235j/OSVR-Core,godbyk/OSVR-Core,Armada651/OSVR-Core,feilen/OSVR-Core,d235j/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,feilen/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,leemichaelRazer/OSVR-Core,feilen/OSVR-Core,d235j/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,d235j/OSVR-Core,Armada651/OSVR-Core,Armada651/OSVR-Core,OSVR/OSVR-Core,Armada651/OSVR-Core,leemichaelRazer/OSVR-Core,d235j/OSVR-Core,godbyk/OSVR-Core