work around nan() not propagating its argument with nVidia OpenCL

And added a check for this to cl-test.ods .

Change-Id: I9b62f2cbef46d5b3dc0adda2b97dda9b8465fe88
Reviewed-on: https://gerrit.libreoffice.org/63174
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

sc/source/core/opencl/formulagroupcl.cxx

@@ -47,6 +47,13 @@ static const char* const publicFunc =
  "\n"
  "double CreateDoubleError(ulong nErr)\n"
  "{\n"
+ // nVidia OpenCL, at least on Linux, seems to ignore the argument to nan(),
+ // so using that would not propagate the type of error, work that around
+ // by directly constructing the proper IEEE double NaN value
+ // TODO: maybe use a better way to detect such systems?
+ "#ifdef cl_nv_pragma_unroll\n"
+ "    return as_double(0x7FF8000000000000+nErr);\n"
+ "#endif\n"
  "    return nan(nErr);\n"
  "}\n"
  "\n"