- Support the case of degenerate dimensions that are not used by the
  variables being read.
- Support degenerate dimensions that are being used by the variables
  regardless of the numerical position of the degenerate dimension.
  For example, if T is the degenerate dimension, support reading
  Y,X,T or T,Y,X.

Both changes are needed to support the reading of climatologies from the
NMME climatology datasets published by NOAA.