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.