Add option to use clew to manually open the OpenCL dynamic library

fix Linux build of App_Bullet3_OpenCL_Demos. Unfortunately the simulation doesn't work properly, need to fix it
(and add unit tests)

test/OpenCL/ParallelPrimitives/premake4.lua

@@ -35,7 +35,8 @@ function createProject(vendor)
 	end
 end
 
+createProject("clew")
 createProject("AMD")
 createProject("Intel")
 createProject("NVIDIA")
-createProject("Apple")
+createProject("Apple")