Test the value of HAVE_CXX, not presence of definition.
Test the value of HAVE_CXX, not presence of definition.

bitfusionio/Oclgrind,surround-io/oclgrind,mpflanzer/Oclgrind,surround-io/oclgrind,mpflanzer/Oclgrind,bitfusionio/Oclgrind,surround-io/oclgrind,mpflanzer/Oclgrind,mpflanzer/Oclgrind,surround-io/oclgrind,bitfusionio/Oclgrind,bitfusionio/Oclgrind