cmake HAVE_DISPATCH examples

NCAR/ParallelIO CMakeLists.txt :388

CHECK_C_SOURCE_COMPILES("
#include <netcdf_meta.h>
#if NC_DISPATCH_VERSION < 2
      choke me
#endif
#if NC_DISPATCH_VERSION > 5
    choke me
#endif
int main() {return 0;}" HAVE_DISPATCH)