Log Message:
Update to 1.6.17:

Version 1.6.17beta01 [January 29, 2015]
  Removed duplicate PNG_SAFE_LIMITS_SUPPORTED handling from pngconf.h
  Corrected the width limit calculation in png_check_IHDR().
  Removed user limits from pngfix. Also pass NULL pointers to
    png_read_row to skip the unnecessary row de-interlace stuff.
  Added testing of png_set_packing() to pngvalid.c
  Regenerated configure scripts in the *.tar distributions with libtool-2.4.4
  Implement previously untested cases of libpng transforms in pngvalid.c
  Fixed byte order in 2-byte filler, in png_do_read_filler().
  Made the check for out-of-range values in png_set_tRNS() detect
    values that are exactly 2^bit_depth, and work on 16-bit platforms.
  Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
  Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
    pngset.c to avoid warnings about dead code.
  Added "& 0xff" to many instances of expressions that are typecast
    to (png_byte), to avoid Coverity gripes.

Version 1.6.17beta02 [February 7, 2015]
  Work around one more Coverity-scan dead-code warning.
  Do not build png_product2() when it is unused.

Version 1.6.17beta03 [February 17, 2015]
  Display user limits in the output from pngtest.
  Eliminated the PNG_SAFE_LIMITS macro and restored the 1-million-column
    and 1-million-row default limits in pnglibconf.dfa, that can be reset
    by the user at build time or run time.  This provides a more robust
    defense against DOS and as-yet undiscovered overflows.

Version 1.6.17beta04 [February 21, 2015]
  Added PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED macro, on by default.
  Allow user to call png_get_IHDR() with NULL arguments (Reuben Hawkins).
  Rebuilt configure scripts with automake-1.15 and libtool-2.4.6

Version 1.6.17beta05 [February 25, 2015]
  Restored compiling of png_reciprocal2 with PNG_NO_16BIT.

Version 1.6.17beta06 [February 27, 2015]
  Moved png_set_filter() prototype into a PNG_WRITE_SUPPORTED block
    of png.h.
  Avoid runtime checks when converting integer to png_byte with
    Visual Studio (Sergey Kosarevsky)

Version 1.6.17rc01 [March 4, 2015]
  No changes.

Version 1.6.17rc02 [March 9, 2015]
  Removed some comments that the configure script did not handle
    properly from scripts/pnglibconf.dfa and pnglibconf.h.prebuilt.
  Free the unknown_chunks structure even when it contains no data.

Version 1.6.17rc03 [March 12, 2015]
  Updated CMakeLists.txt to add OSX framework, change YES/NO to ON/OFF
    for consistency, and remove some useless tests (Alexey Petruchik).

Version 1.6.17rc04 [March 16, 2015]
  Remove pnglibconf.h, pnglibconf.c, and pnglibconf.out instead of
    pnglibconf.* in "make clean" (Cosmin).
  Fix bug in calculation of maxbits, in png_write_sBIT, introduced
    in libpng-1.6.17beta01 (John Bowler).

Version 1.6.17rc05 [March 21, 2015]
  Define PNG_FILTER_* and PNG_FILTER_VALUE_* in png.h even when WRITE
    is not supported (John Bowler).  This fixes an error introduced in
    libpng-1.6.17beta06.
  Reverted "& 0xff" additions of version 1.6.17beta01. Libpng passes
    the Coverity scan without them.

Version 1.6.17rc06 [March 23, 2015]
  Remove pnglibconf.dfn and pnglibconf.pre with "make clean".
  Reformatted some "&0xff" instances to "& 0xff".
  Fixed simplified 8-bit-linear to sRGB alpha. The calculated alpha
    value was wrong.  It's not clear if this affected the final stored
    value; in the obvious code path the upper and lower 8-bits of the
    alpha value were identical and the alpha was truncated to 8-bits
    rather than dividing by 257 (John Bowler).

Version 1.6.17 [March 26, 2015]
  No changes.