//bugs.freedesktop.org/show_bug.cgi?id=2879) attachment #2556
(https://bugs.freedesktop.org/attachment.cgi?id=2556) Refix for bug
2879 - downgrade 15bit PseudoColor to 14bit - the current datatype for
the |ColormapEntries| is a |signed short| which is too small for
|32768| colors (=integer overflow).