Log Message:
Update to 1.6.3:

Changes since the last public release (1.6.2):

  Revised stack marking in arm/filter_neon.S and configure.ac.
  Ensure that NEON filter stuff is completely disabled when switched 'off'.
    Previously the ARM NEON specific files were still built if the option
    was switched 'off' as opposed to being explicitly disabled.
  Test for 'arm*' not just 'arm' in the host_cpu configure variable.
  Rebuilt the configure scripts.
  Expanded manual paragraph about writing private chunks, particularly
    the need to call png_set_keep_unknown_chunks() when writing them.
  Avoid dereferencing NULL pointer possibly returned from
     png_create_write_struct() (Andrew Church).
  Calculate our own zlib windowBits when decoding rather than trusting the
    CMF bytes in the PNG datastream.
  Added an option to force maximum window size for inflating, which was
    the behavior of libpng15 and earlier.
  Added png-fix-itxt and png-fix-too-far-back to the built programs and
    removed warnings from the source code and timepng that are revealed as
    a result.
  Detect wrong libpng versions linked to png-fix-too-far-back, which currently
    only works with libpng versions that can be made to reliably fail when
    the deflate data contains an out-of-window reference.  This means only
    1.6 and later.
  Fixed gnu issues: g++ needs a static_cast, gcc 4.4.7 has a broken warning
    message which it is easier to work round than ignore.
  Updated contrib/pngminus/pnm2png.c (Paul Stewart):
    Check for EOF
    Ignore "#" delimited comments in input file to pnm2png.c.
    Fixed whitespace handling
    Added a call to png_set_packing()
    Initialize dimension values so if sscanf fails at least we have known
      invalid values.
  Attempt to detect configuration issues with png-fix-too-far-back, which
    requires both the correct libpng and the correct zlib to function
    correctly.
  Check ZLIB_VERNUM for mismatches, enclose #error in quotes
  Added information in the documentation about problems with and fixes for
    the bad CRC and bad iTXt chunk situations.
  Allow contrib/pngminus/pnm2png.c to compile without WRITE_INVERT and
    WRITE_PACK supported (writes error message that it can't read P1 or
  Improved png-fix-too-far-back usage message, added --suffix option.
  Revised contrib/pngminim/*/makefile to generate pnglibconf.h with the
    right zlib header files.
  Separated CPPFLAGS and CFLAGS in contrib/pngminim/*/makefile
  Removed a redundant test in png_set_IHDR().
  Added set(CMAKE_CONFIGURATION_TYPES ...) to CMakeLists.txt (Andrew Hundt)
  Deleted set(CMAKE_BUILD_TYPE) block from CMakeLists.txt
  Enclose the prototypes for the simplified write API in
    #ifdef PNG_STDIO_SUPPORTED/#endif
  Make ARM NEON support work at compile time (not just configure time).
    This moves the test on __ARM_NEON__ into pngconf.h to avoid issues when
    using a compiler that compiles for multiple architectures at one time.
  Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from
    pnglibconf.h, allowing more of the decisions to be made internally
    (pngpriv.h) during the compile.  Without this, symbol prefixing is broken
    under certain circumstances on ARM platforms.  Now only the API parts of
    the optimizations ('check' vs 'api') are exposed in the public header files
    except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
    decision about whether or not to use the optimizations.
  Protect symbol prefixing against CC/CPPFLAGS/CFLAGS useage.
    Previous iOS/Xcode fixes for the ARM NEON optimizations moved the test
    on __ARM_NEON__ from configure time to compile time.  This breaks symbol
    prefixing because the definition of the special png_init_filter_functions
    call was hidden at configure time if the relevant compiler arguments are
    passed in CFLAGS as opposed to CC.  This change attempts to avoid all
    the confusion that would result by declaring the init function even when
    it is not used, so that it will always get prefixed.
  Revised libpng.3 so that "doclifter" can process it.
  Revised example.c to illustrate use of PNG_DEFAULT_sRGB and
PNG_GAMMA_MAC_18
    as parameters for png_set_gamma().  These have been available since
    libpng-1.5.4.
  Renamed contrib/tools/png-fix-too-far-back.c to pngfix.c and revised it
    to check all compressed chunks known to libpng.
  Updated documentation to show default behavior of benign errors correctly.
  Only compile ARM code when PNG_READ_SUPPORTED is defined.
  Fixed undefined behavior in contrib/tools/pngfix.c and added new strip
    option. pngfix relied on undefined behavior and even a simple change from
    gcc to g++ caused it to fail.  The new strip option 'unsafe' has been
    implemented and is the default if --max is given.  Option names have
    been clarified, with --strip=transform now stripping the bKGD chunk,
    which was stripped previously with --strip=unused.
  Added all documented chunk types to pngpriv.h
  Unified pngfix.c source with libpng17.
  Revised manual about changes in iTXt chunk handling made in libpng-1.6.0.
  Added "/* SAFE */" comments in pngrutil.c and pngrtran.c where warnings
    may be erroneously issued by code-checking applications.