OpenEXR fix: was botching ordering of per-channel data formats because
of the channel order scrambling that happens when reading OpenEXR files.
oiiotool -d enhancement: -d CHAN=TYPE sets for just one channel.

Clarification of oiiotool -d command:

As before, -d TYPE sets the data type for subsequent image output, for
all channels.

New: -d CHAN=TYPE overrides the data type for a particular named
channel.  This also lets oiiotool, for the first time, easily specify
that its output should have different per-channel data types (if the
output file format supports it).

Example: if you have an rgbaz file, all float channels, you can convert
it to a file where rgba are half and z is float:
    oiiotool rgbaz.exr -d half -d Z=float -o rgbaz2.exr
(Note that OpenEXR is one of the few formats that can support this.)