Log Message:
Bump suse100_libpng to 4.
Update libpng from 1.2.8-5.2 to 1.2.8-5.6.

5.4:
Applications using libpng can crash if libpng is ask to
process a grayscale image with a malformed (bad CRC) tRNS
chunk. (CVE-2007-2445)

5.6:
Description: Speciall crafted png files could crash applications when attempting
to open such a file (CVE-2007-5269).