Log Message:
Updated png to 1.6.25.

Changes since the last public release (1.6.24):
  Reject oversized iCCP profile immediately.
  Cleaned up PNG_DEBUG compile of pngtest.c.
  Conditionally compile png_inflate().
  Don't install pngcp; it conflicts with pngcp in the pngtools package.
  Minor editing of INSTALL, (whitespace, added copyright line)
  Added MIPS support (Mandar Sahastrabuddhe \ 
<Mandar.Sahastrabuddhe@imgtec.com>).
  Rebased contrib/intel/intel_sse.patch after the MIPS implementation.