Changes made to pristine libpng source by mozilla.org developers.

2016/01/16  -- Synced with libpng-1.6.21 (bug #1230757).

2015/11/12  -- Synced with libpng-1.6.19 (bug #1224244).

2015/07/30  -- Synced with libpng-1.6.18 (bug #1186977).

2015/03/27  -- Synced with libpng-1.6.17 (bug #1147909).

2014/12/22  -- Synced with libpng-1.6.16 (bug #1114360).
               Added arm.patch file.

2014/11/20  -- Synced with libpng-1.6.15 (bug #1102523).

2014/10/23  -- Synced with libpng-1.6.14 (bug #1087841).

2014/08/21  -- Synced with libpng-1.6.13 (bug #1021713).
               Renamed mozpngconf.h to pnglibconf.h.
               Revised system arm/filter_neon.S to include the lines
               #define PNG_READ_SUPPORTED and  #define MOZ_PNG_HAVE_ARM_NEON
               because the moz.build system doesn't yet pass -DDefined
               macros to the assembler.

2014/03/21  -- Synced with libpng-1.6.10 (bug #980488) and disabled
               PNG_WARNINGS and PNG_ERROR_TEXT in non-debug builds.
               Limit image dimensions to 32767 (bug #251381, #591822,
               and #967656).

2014/03/04  -- Enabled PNG_WARNINGS and other stuff in mozpngconf.h
               as part of enabling Freetype2 with PNG (bug #969814).

2014/03/03  -- Fixed hang with empty IDAT (bug #974825). This will be
               fixed in libpng-1.6.10.

2014/02/18  -- Exposed png_error(), etc. redefinitions to applications
               (moved them from pngpriv.h to png.h). This will be fixed
               in libpng-1.6.10.

2014/02/18  -- Disabled PNG_FIXED_POINT_SUPPORTED in mozpngconf.h (we
               don't need both FIXED and FLOATING_POINT support).

2014/02/15  -- Synced with libpng-1.6.9 (bug #952505).

2014/02/11  -- Fixed crash with empty PLTE, CVE-2013-6954 (bug #945912).
               This will be fixed in libpng-1.6.9.

2013/12/11  -- Enable ARM support (bug #832390).

2013/11/17  -- Synced with libpng-1.6.7 (bug #938740).

2013/09/21  -- Synced with libpng-1.6.6 (bug #841734).

2013/07/17  -- Synced with libpng-1.5.17 (bug #886499).

2013/06/06  -- Synced with libpng-1.5.16 (bug #873001).

2013/04/11  -- Synced with libpng-1.5.15 (bug #858578).

2013/01/24  -- Synced with libpng-1.5.14 (bug #832487).

2013/01/23  -- Disabled TEXT support in mozpngconf.h (bug #833594).

2012/10/02  -- Synced with libpng-1.5.13 (bug #775662).

2012/07/16  -- Add an "APNG-aware app" flag (bug #759067).

2012/07/04  -- Synced with libpng-1.5.11 (bug #771394).

2012/04/13  -- Synced with libpng-1.5.10 (bug #745178).

2012/02/19  -- Synced with libpng-1.5.9 (bug #648690).

2011/07/20  -- Synced with libpng-1.4.8 (bug #669863).

2011/04/08  -- Synced with libpng-1.4.7 (bug #624133).

2010/06/30  -- Synced with libpng-1.4.3 (bug #564792).

2010/02/26  -- Synced with libpng-1.4.1 (bug #544747).

2010/01/04  -- Synced with libpng-1.4.0 (bug #532645).

2009/09/10  -- Synced with libpng-1.2.40 (bug #492200 and #504805).
               Moved location of acTL chunk to just after IHDR
               in output PNG file.

2009/06/01  -- Eliminated incorrect test and rejection of APNG
               blend_op in opaque images (bug #441971 and #455140).

2009/05/17  -- Always clear prev_row for each APNG frame (bug #463465).

2009/02/19  -- Synced with libpng-1.2.35 (bug #478901).

2008/08/21  -- Synced with libpng-1.2.31 (bug #418900).

2008/03/29  -- Initialize prev_row for each APNG frame, only when
               the frame size increases (bug #420416).

2008/01/18  -- Synced with libpng-1.2.24 (bug #408429).

2007/11/13  -- Synced with libpng-1.2.23; Removed pnggccrd.c and pngvcrd.c;
               Reduced footprint by removing error and warning text in
               non-debug builds via settings in mozpngconf.h (bug #403239).

2007/11/06  -- Synced with libpng-1.2.22 (removes MMX support) (bug #386585).

2007/07/27  -- Enabled cHRM and iCCP chunks for color management (bug #16769).

2007/05/05  -- Zeroed png_ptr->num_trans on CRC error (bug #374810).

2007/04/19  -- Synced with libpng-1.2.16 tree (bug #373249).

2007/03/20  -- Added support for APNG (bug #257197).

2006/06/27  -- Synced with libpng-1.2.12 tree (bug #334110).

2004/10/07  -- Synced with libpng-1.2.7 tree (bug #261922).

2004/10/07  -- Added mozpngconf.h (bug #208607).