Signature:
  SUBROUTINE h5pget_virtual_printf_gap_f(dapl_id, gap_size, hdferr)
    INTEGER(HID_T)  , INTENT(IN)  :: dapl_id
    INTEGER(HSIZE_T), INTENT(OUT) :: gap_size
    INTEGER         , INTENT(OUT) :: hdferr
Inputs:
  dapl_id    - Dataset access property list identifier for the virtual dataset
Outputs:
  gap_size - Maximum number of the files and/or datasets allowed to 
             be missing for determining the extent of an unlimited virtual 
             dataset with printf-style mappings. 
  hdferr   - Returns 0 if successful and -1 if fails