OpenSubdiv: Fix error found by PerfectionCat,

Use glew, not gl constants to detect presence of extensions.
glProgramParameterEXTi is part of GLEW_EXT_geometry_shader4

intern/opensubdiv/opensubdiv_capi.cc

@@ -296,8 +296,7 @@ const struct OpenSubdiv_TopologyRefinerDescr *openSubdiv_getGLMeshTopologyRefine
 
 int openSubdiv_supportGPUDisplay(void)
 {
-	return GL_EXT_geometry_shader4 &&
-	       GL_ARB_gpu_shader5 &&
-	       GL_ARB_uniform_buffer_object &&
-	       glProgramParameteriEXT;
+	return GLEW_EXT_geometry_shader4 &&
+	       GLEW_ARB_gpu_shader5 &&
+	       GLEW_ARB_uniform_buffer_object;
 }