Only #define PNG_DEPSTRUCT, etc. in pngconf.h if not already defined.

  Added PNG_DEPSTRUCT, PNG_DEPRECATED, PNG_USE_RESULT, PNG_NORETURN, and
    PNG_ALLOCATED macros to detect deprecated direct access to the
    png_struct or info_struct members and other deprecated usage in
    applications (John Bowler).
  Added -DPNG_CONFIGURE_LIBPNG to the makefile CFLAGS, to prevent warnings
    about direct access to png structs by libpng functions while building
    libpng.
  Removed three direct references to read_info_ptr members in pngtest.c
    that were detected by the new PNG_DEPSTRUCT macro.
  Moved the png_debug macro definitions and the png_read_destroy(),
    png_write_destroy() and png_far_to_near() prototypes from png.h
    to pngpriv.h (John Bowler)
  Moved the synopsis lines for png_read_destroy(), png_write_destroy()
    png_debug(), png_debug1(), and png_debug2() from libpng.3 to libpngpf.3.

instead of between 1.2.41 and 1.4.0 in documentation.

for supporting WindowsCE.

WindowsCE does not provide the "tm" structure.

and merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.

from pngwrite.c

(Contributed by Philip Lowman)

in png_handle_sPLT().

to check info_ptr members instead of the contents of the returned parameters.