libpng security update

libpng:
[2:1.2.7-8]

• Remove incorrect fix for CVE-2011-2690; that bug doesn’t exist in 1.2.7
  Resolves: #721302
  [2:1.2.7-7]
• Back-port fixes for CVE-2011-2690, CVE-2011-2692
  Note: CVE-2011-2691, announced at the same time, does not apply to 1.2.7;
  likewise for CVE-2011-2501
  Resolves: #721302
  libpng10:
  [1.0.16-9]
• Remove incorrect fix for CVE-2011-2690; that bug doesn’t exist in 1.0.16
  Resolves: #721308
  [1.0.16-8]
• Back-port fixes for CVE-2011-2690, CVE-2011-2692
  Note: CVE-2011-2691, announced at the same time, does not apply to 1.0.16;
  likewise for CVE-2011-2501
  Resolves: #721308