One point about the "custom readouts" etc --- I'm asuming that the
all definitions for the CCD windowing will be available for editing by
the user, that is, CCDROTYP=LONGSLIT will have a default windowing
configuration, set by us, but the user will be able to modify it to his/her
taste.  Thus, CCDROTYP=CUSTOM can refer to something quite special since
it will not be required for slight customizations from the defaults
for the standard modes.  Under this scheme, in principle, there could be
4 custom readouts defined, call DIRECT,SPECTR,LONGSLIT and CUSTOM. In
practice, we _hope_ the user will honor the intent of the first three names.