Add other NetCDF variants in PIO code.

* These modes do not all work immediately but will later on.

src/pio_server.c

@@ -1073,6 +1073,8 @@ cdiPioServerStreamOpen(const char *filename, char filemode, int filetype, stream
   switch (filetype)
     {
 #if defined HAVE_LIBNETCDF && !defined HAVE_PARALLEL_NC4
+    case CDI_FILETYPE_NC:
+    case CDI_FILETYPE_NC2:
     case CDI_FILETYPE_NC4:
     case CDI_FILETYPE_NC4C:
       {