to avoid compiler complaints about doubly declaring things "const".

about fixing the "#if def " bug

("#if def" should be "#ifdef")

to give Dennis Gustafsson credit for noticing the incorrect typecast
of "filler".

and always use png_calloc().  The macros were only there for testing,
since libpng-1.4.0beta48 and no problems have been reported.

from contrib/visupng and contrib/pngminim sources.

Always use local arrays, which has been the default behavior
for a long time.

instead of memset to zero in png_read_png().

They were only useful for obtaining compatibility for old applications
that used libpng-1.0.x versions prior to the implementation of "free_me".

except in pngconf.h where they can be used to request that
PNG_FEATURE_SUPPORTED not be defined.

It does not seem to promise any benefit to libpng.

To try this, configure libpng using PNG_USE_MEMSET_LOOP.  Initial testing
with pngcrush was not promising, although it does save a hundred bytes or
so of executable size.

1. Modify project(PNG) to project(PNG C) to avoid search for C++ compiler
2. set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS true) and fix end conditionals
from ugly else(FOO AND BAR) endif(FOO AND BAR) to else() endif()
3. Add missing include_directories() for ZLIB_INCLUDE_DIR
4. Created CMake options to allow configurable building of STATIC or SHARED
libpng, both default on.
5. Modified PNG_DEBUG to default to false?
6. Fix installation of static/shared libraries so DLL goes in prefix+/bin,
all others in prefix+/lib

to reflect the new set of files in the distribution.

lpXYZ.tar.bz2 (with CRLF), KNOWNBUG, libpng-x.y.z-KNOWNBUG.txt,
and the "noconfig" files have been removed from the distribution.

It had been put inside the png_debug2() statement.

PNG_UNKNOWN_CHUNK_SUPPORTED should be PNG_HANDLE_AS_UNKNOWN_SUPPORTED.