Consolidation with CDI-PIO (develop)

Generally, this is !11 (merged) rebased onto the develop branch.

This is the first develop-based version accepted by the Buildbot of ICON: https://buildbot.dkrz.de/grid?branch=m300488/cdi-pio-2-integration

tests/simple_model_helper.h

@@ -23,7 +23,11 @@ void var_scale(int datatype, double *mscale, double *mrscale);
 static inline double
 sign_flat(double v)
 {
+#ifdef _CRAYC
+  if (v == 0 && copysign(1.0, v) < 0.0) return 0.0;
+#else
   if (!(v < 0.0 || v > 0.0)) return 0.0;
+#endif
   //    if (v == 0.0) return 0.0;
   return v;
 }