or intrinsics to be turned on during the build by defining
PNG_ARM_NEON_IMPLEMENTATION to the correct value (2 or 1).  The
default is "undefined" and the build type is selected in pngpriv.h.

We use -mfpu=neon instead of a configuration flag.

pngpriv.h and detect the broken GCC compilers.

it can manage, limited by the number of rows.

Use filter_neon_intrinsics.c in preference to filter_neon.S when possible.

pngrtran.c

continuation backslashes

if PNG_READ_SUPPORTED and PNG_ARM_NEON_OPT > 0

arm/filter_neon_intrinsics.c; enable with configuration flag
PNG_ARM_NEON_INTRINSICS.

by always removing the 1.14 'compile' script but never checking for it.

the useful side effect of avoiding a bogus warning generated by the latest
version of the Intel C compiler (it objects to
condition ? string-literal : string-literal).

the Intel C compiler complains about casting a string literal as (char*), so
copied the treatment of z_const from the library code into pngfix.c

    1) Added the 'compile' program to the list of programs that must be cleaned
       in autogen.sh
    2) Added 'subdir-objects' which causes .c files in sub-directories to be
       compiled such that the corresponding .o files are also in the
       sub-directory.  This is because automake 1.14 warns that the
       current behavior of compiling to the top level directory may be removed
       in the future.
    3) Updated dependencies on pnglibconf.h to match the new .o locations and
       added all the files in contrib/libtests and contrib/tools that depend
       on pnglibconf.h
    4) Added 'BUILD_SOURCES = pnglibconf.h'; this is the automake recommended
       way of handling the dependencies of sources that are machine generated;
       unfortunately it only works if the user does 'make all' or 'make check',
       so the dependencies (3) are still required.

requirements of png_modifier are greater than that of png_store and as a
consequence compilation of pngvalid.c results in a warning about increased
alignment requirements because of the bare cast to (png_modifier*). The code
is safe, because the pointer is known to point to a stack allocated
png_modifier, but this change avoids the warning.

  Fixed default behavior of ARM_NEON_API. If the ARM NEON API option was
    compiled without the CHECK option it defaulted to on, not off.

  Check user callback behavior in pngunknown.c. Previous versions compiled
    if SAVE_UNKNOWN was not available but did nothing since the callback
    was never implemented.

  Merged pngunknown.c with 1.7 version and back ported 1.7 improvements/fixes

off. Also fixed the pngminim makefiles to work when $(MAKEFLAGS) contains stuff
which terminates the make options (as by default in recent versions of Gentoo).

png_chunk_unknown_handling() function, and restored the unknown-chunk
handling code from libpng-1.6.6.

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breaks 'NOREAD' builds.