Bug fixes:

• images with an translucent alpha channel were not scaled correctly by the default (qtype=normal) scaling method. RT #62933

• Imager::Color::Float now translates "#FFFFFF" to white instead of just a little darker.

• make the default color map build algorithm "mediancut". This changes the default color map builder for writing GIFs back to what it was in 0.77, reverting a performance regression. RT #64785