Log Message:
Updated png to 1.6.32.

Version 1.6.32beta01 [July 31, 2017]
  Avoid possible NULL dereference in png_handle_eXIf when benign_errors
    are allowed. Avoid leaking the input buffer "eXIf_buf".
  Eliminated png_ptr->num_exif member from pngstruct.h and added num_exif
    to arguments for png_get_eXIf() and png_set_eXIf().
  Added calls to png_handle_eXIf(() in pngread.c and png_write_eXIf() in
    pngwrite.c, and made various other fixes to png_write_eXIf().
  Changed name of png_get_eXIF and png_set_eXIf() to png_get_eXIf_1() and
    png_set_eXIf_1(), respectively, to avoid breaking API compatibility
    with libpng-1.6.31.

Version 1.6.32beta02 [August 1, 2017]
  Updated contrib/libtests/pngunknown.c with eXIf chunk.

Version 1.6.32beta03 [August 2, 2017]
  Initialized btoa[] in pngstest.c
  Stop memory leak when returning from png_handle_eXIf() with an error
    (Bug report from the OSS-fuzz project).

Version 1.6.32beta04 [August 2, 2017]
  Replaced local eXIf_buf with info_ptr-eXIf_buf in png_handle_eXIf().
  Update libpng.3 and libpng-manual.txt about eXIf functions.

Version 1.6.32beta05 [August 2, 2017]
  Restored png_get_eXIf() and png_set_eXIf() to maintain API compatability.

Version 1.6.32beta06 [August 2, 2017]
  Removed png_get_eXIf_1() and png_set_eXIf_1().

Version 1.6.32beta07 [August 3, 2017]
  Check length of all chunks except IDAT against user limit to fix an
    OSS-fuzz issue.

Version 1.6.32beta08 [August 3, 2017]
  Check length of IDAT against maximum possible IDAT size, accounting
    for height, rowbytes, interlacing and zlib/deflate overhead.
  Restored png_get_eXIf_1() and png_set_eXIf_1(), because strlen(eXIf_buf)
    does not work (the eXIf chunk data can contain zeroes).

Version 1.6.32beta09 [August 3, 2017]
  Require cmake-2.8.8 in CMakeLists.txt. Revised symlink creation,
    no longer using deprecated cmake LOCATION feature (Clifford Yapp).
  Fixed five-byte error in the calculation of IDAT maximum possible size.

Version 1.6.32beta10 [August 5, 2017]
  Moved chunk-length check into a png_check_chunk_length() private
    function (Suggested by Max Stepin).
  Moved bad pngs from tests to contrib/libtests/crashers
  Moved testing of bad pngs into a separate tests/pngtest-badpngs script
  Added the --xfail (expected FAIL) option to pngtest.c. It writes XFAIL
    in the output but PASS for the libpng test.
  Require cmake-3.0.2 in CMakeLists.txt (Clifford Yapp).
  Fix "const" declaration info_ptr argument to png_get_eXIf_1() and the
    num_exif argument to png_get_eXIf_1() (Github Issue 171).

Version 1.6.32beta11 [August 7, 2017]
  Added "eXIf" to "chunks_to_ignore[]" in \ 
png_set_keep_unknown_chunks().
  Added huge_IDAT.png and empty_ancillary_chunks.png to testpngs/crashers.
  Make pngtest --strict, --relax, --xfail options imply -m (multiple).
  Removed unused chunk_name parameter from png_check_chunk_length().
  Relocated setting free_me for eXIf data, to stop an OSS-fuzz leak.
  Initialize profile_header[] in png_handle_iCCP() to fix OSS-fuzz issue.
  Initialize png_ptr->row_buf[0] to 255 in png_read_row() to fix OSS-fuzz UMR.
  Attempt to fix a UMR in png_set_text_2() to fix OSS-fuzz issue.
  Increase minimum zlib stream from 9 to 14 in png_handle_iCCP(), to account
    for the minimum 'deflate' stream, and relocate the test to a point
    after the keyword has been read.
  Check that the eXIf chunk has at least 2 bytes and begins with "II" \ 
or "MM".

Version 1.6.32rc01 [August 18, 2017]
  Added a set of "huge_xxxx_chunk.png" files to contrib/testpngs/crashers,
    one for each known chunk type, with length = 2GB-1.
  Check for 0 return from png_get_rowbytes() and added some (size_t) typecasts
    in contrib/pngminus/*.c to stop some Coverity issues (162705, 162706,
    and 162707).
  Renamed chunks in contrib/testpngs/crashers to avoid having files whose
    names differ only in case; this causes problems with some platforms
    (github issue #172).

Version 1.6.32rc02 [August 22, 2017]
  Added contrib/oss-fuzz directory which contains files used by the oss-fuzz
    project (https://github.com/google/oss-fuzz/tree/master/projects/libpng).

Version 1.6.32 [August 24, 2017]
  No changes.