typecast (unsigned int) in png.c
typecast (unsigned int) in png.c


git-svn-id: 97b2d82d3d182ea4f30be26e4515d280eb22ffdc@5496 aa41f4f7-0bf4-0310-aa73-e5a19afd5a74

Distrotech/ImageMagick,Distrotech/ImageMagick,Distrotech/ImageMagick,Distrotech/ImageMagick