xgamma.icn: Program to configure X color correction

Xgamma sets the root window properties that provide device-independent
color under X windows.  Icon derives the default value of the "gamma"
attribute from these properties.

Ideally, color properties would be set automatically based on
specifications provided by the manufacturer of the monitor.
Lacking such specifications, xgamma synthesizes intensity ramps
for an ideal monitor characterized by a given gamma value.

The phosphor colors, which must also be set, are set to those of a
Sony Trinitron monitor based on values from the X11R5 distribution.

There are three ways to call xgamma:

     xgamma m.n      set color properties using gamma value m.n
     xgamma none     remove color properties
     xgamma          report gamma attribute inferred by Icon

A pipe to "xcmsdb" is opened, so that program must be in the current
search path.

The default gamma attribute calculated by Icon does not always exactly
match the value set by xgamma.  The reason for this is unclear.