fix: In Linux CL/GL sharing, handle failed symbols lookup

[smunaut]

In some cases we endup with GL being found but neither GLX or EGL found and this currently leads to crash.

So to better handle this case (and others), we keep track if we found symbols or not.

If we're asked if CL/GL sharing is supported we check the load worked.

If it's during an actual context creation we check what we were given match what we could load and fail context property finalization if not.

If it's during an "info" request where we don't have any properties yet, we return yes if either GLX or EGL was found.

[JablonskiMateusz]

please update years in copyright headers

[smunaut]

Done

[JablonskiMateusz]

please correct tests as well, as currently there is unit test failure:

../neo/opencl/test/unit_test/sharings/gl/linux/gl_sharing_enable_tests.cpp:172: Failure
Value of: res
  Actual: false
Expected: true


../neo/opencl/test/unit_test/sharings/gl/linux/gl_sharing_enable_tests.cpp:173: Failure
Expected equality of these values:
  0
  errcodeRet
    Which is: -64


../neo/opencl/test/unit_test/sharings/gl/linux/gl_sharing_enable_tests.cpp:176: Failure
Expected: (nullptr) != (sharing), actual: (nullptr) vs NULL