OK, I fixed cl.hpp file to not include gl.h. We do not support OpenCL-OpenGL interoperability anyway, so there is no need to include that. Overwrite C:/altera/14.0/hld/host/include/CL/cl.hpp with attached cl.hpp.txt (make sure it's still called cl.hpp, I couldn't attach a file with .hpp extension).
I tested a simple program that includes cl.hpp and it failed as you described before the change and compiles with the change.
You can also use a random gl.hpp that you found, as long as you don't actually use any of the GL-related functions.
We'll fix this in the new release of the tool. Thanks a lot for letting us know!