Signature:
  SUBROUTINE h5pget_virtual_count_f(dcpl_id, count, hdferr)
    INTEGER(HID_T), INTENT(IN)   :: dcpl_id
    INTEGER(SIZE_T), INTENT(OUT) :: count
    INTEGER, INTENT(OUT)         :: hdferr
Inputs:
  dcpl_id - The identifier of the virtual dataset creation property list. 
Outputs:
  count   - The number of mappings.
  hdferr  - Returns 0 if successful and -1 if fails