Consider retiring OpenSubdiv/cmake/FindGLEW.cmake

[davidgyu]

trafficstars

Now that CMake 3.x supports FindGLEW by default: https://cmake.org/cmake/help/v3.0/module/FindGLEW.html

[meshula]

+1 :)

[davidgyu]

Same for FindOpenCL as of CMake 3.1: https://cmake.org/cmake/help/v3.1/module/FindOpenCL.html

[jtran56]

Filed as internal issue #142044.