Fixed vtrViewer build errors on OS X.
Fixed vtrViewer build errors on OS X.

poljere/OpenSubdiv,xldeveloper/OpenSubdiv,takahito-tejima/OpenSubdiv,nyotis/OpenSubdiv,c64kernal/OpenSubdiv,poljere/OpenSubdiv,nyotis/OpenSubdiv,shengfuintel/OpenSubdiv,lookup1980/OpenSubdiv,takahito-tejima/OpenSubdiv,nyotis/OpenSubdiv,poljere/OpenSubdiv,takahito-tejima/OpenSubdiv,lookup1980/OpenSubdiv,c64kernal/OpenSubdiv,shengfuintel/OpenSubdiv,anshuarya/OpenSubdiv,anshuarya/OpenSubdiv,anshuarya/OpenSubdiv,shengfuintel/OpenSubdiv,xldeveloper/OpenSubdiv,c64kernal/OpenSubdiv,lookup1980/OpenSubdiv,xldeveloper/OpenSubdiv