Source file gathering is now done in the makefile.

is defined.  We are considering removing it entirely.

options.  This makes the installed pnglibconf.h more readable but causes no
other change.  The intention is that users of libpng will find it
easier to understand if an API they need is missing.

The API declaration in png.h is removed if both READ and WRITE USER_TRANSFORM
are turned off but was left defined in pngtrans.c

to PNG_HANDLE_AS_UNKNOWN_SUPPORTED in gregbook/readpng2.c

    The macro was documented with two arguments (name,ordinal), however
    the symbol checking .dfn files assumed five arguments.  The five
    argument form seems more useful so it is changed to that.

in pngusr.dfa.

because it has a macro equivalent.

contrib/pngminim/decoder/pngusr.h to make a smaller decoder application.

For Windows/x86 platforms only:
  __stdcall is no longer needed for Visual Basic, so libpng-1.5.0 uses
  __cdecl throughout (both API functions and callbacks) on Windows/x86
  platforms.

This allows the functions
to read and write ints to be disabled independently of PNG_USE_READ_MACROS,
which allows libpng to be built with the functions even though the default
is to use the macros - this allows applications to choose at app build
time whether or not to use macros (previously impossible because the
functions weren't in the default build.)

save some space.

    contrib/pngminim project to pngerror.c, for use when warnings or
    errors are disabled via PNG_NO_WARN or PNG_NO_ERROR_TEXT, to avoid
    storing unneeded error/warning text.