Log Message:
Pullup ticket #4866 - requested by wiz
graphics/png: security fix

Revisions pulled up:
- graphics/png/Makefile                                         1.180
- graphics/png/distinfo                                         1.125

---
   Module Name:	pkgsrc
   Committed By:	wiz
   Date:		Thu Dec  3 15:17:02 UTC 2015

   Modified Files:
   	pkgsrc/graphics/png: Makefile distinfo

   Log Message:
   Update to 1.6.20:

   Version 1.6.20beta01 [November 20, 2015]
     Avoid potential pointer overflow/underflow in png_handle_sPLT() and
       png_handle_pCAL() (Bug report by John Regehr).

   Version 1.6.20beta02 [November 23, 2015]
     Fixed incorrect implementation of png_set_PLTE() that uses png_ptr
       not info_ptr, that left png_set_PLTE() open to the CVE-2015-8126
       vulnerability.

   Version 1.6.20beta03 [November 24, 2015]
     Backported tests from libpng-1.7.0beta69.

   Version 1.6.20rc01 [November 26, 2015]
     Fixed an error in handling of bad zlib CMINFO field in pngfix, found by
       American Fuzzy Lop, reported by Brian Carpenter.  inflate() doesn't
       immediately fault a bad CMINFO field; instead a 'too far back' error
       happens later (at least some times).  pngfix failed to limit CMINFO to
       the allowed values but then assumed that window_bits was in range,
       triggering an assert. The bug is mostly harmless; the PNG file cannot
       be fixed.

   Version 1.6.20rc02 [November 29, 2015]
     In libpng 1.6 zlib initialization was changed to use the window size
       in the zlib stream, not a fixed value. This causes some invalid images,
       where CINFO is too large, to display 'correctly' if the rest of the
       data is valid.  This provides a workaround for zlib versions where the
       error arises (ones that support the API change to use the window size
       in the stream).

   Version 1.6.20 [December 3, 2015]
     No changes. 'correctly' if the rest of the
       data is valid.  This provides a workaround for zlib versions where the
       error arises (ones that support the API change to use the window size
       in the stream).

   Version 1.6.20 [December 3, 2015]
     No changes.