Log Message:
Update to 1.2.31:

version 1.2.31rc01 [August 19, 2008]
  Removed extra crc check at the end of png_handle_cHRM().  Bug introduced
    in libpng-1.2.30beta03 (Heiko Nitzsche).

version 1.2.31rc02 [August 19, 2008]
  Added PNG_WRITE_FLUSH_SUPPORTED block around new png_flush() call.

version 1.2.31rc03 [August 19, 2008]
  Added PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED block, off by default, around
    new png_flush().

version 1.0.39, 1.2.31 [August 21, 2008]
  No changes.

Thanks to Rumko.