Fix mdal build warning unused const var

Author: m-kuhn

external/mdal/frmts/mdal_binary_dat.cpp

@@ -33,8 +33,10 @@ static const int CT_NUMCELLS  = 180;
 static const int CT_NAME      = 190;
 static const int CT_TS        = 200;
 static const int CT_ENDDS     = 210;
+#if 0
 static const int CT_RT_JULIAN = 240;
 static const int CT_TIMEUNITS = 250;
+#endif
 
 static const int CT_2D_MESHES = 3;
 static const int CT_FLOAT_SIZE = 4;