possible png1.5 issue with qt4-libs

[Mark Davies <mark%ecs.vuw.ac.nz@localhost>]

Not sure if this is a subtle png1.5 issue or something else as I have 
limited variants to compare.

Saving a PNG image from KSnapshot or Kolourpaint (kdegraphics4) 
currently gives an image with the colour channels shifted R->G->B and 
red at 255 everywhere.  I think both of these come back to 
QPNGImageWriter::writeImage() from qt4-libs 
src/gui/image/qpnghandler.cpp for the actual writing.

Its working correctly on a NetBSD system with png-1.4.5, 
qt4-libs-4.7.1nb1, and kde-4.5.4 but failing as above on linux and 
NetBSD systems with png-1.5.2, qt4-libs-4.7.2 and kde>=4.5.5

cheers
mark