Diag decimation prototype, fixed masks and cleanup

- The masks for non-native decimated diags were not set right
- Some cleanup of the code to consolidate new calls
- Note that locmask => NULL() shoulbe in the body of subroutines
  not in the definition section. If it is in the definition section
  it is set to null only on the first entry (it is automatically "save"ed)
  and on subsequent entry it is whatever it was the last time.