[libpng17] Revised contrib/pngminim/*/makefile to generate pnglibconf.h with the

right zlib header files.
[libpng17] Added a needed #ifdef/#endif pair.
[libpng17] Updated contrib/pngminus/pnm2png.c (Paul Stewart):

Fixed whitespace handling
Added a call to png_set_packing()
Initialize dimension values so if sscanf fails at least we have known
      invalid values.
[libpng17] Port recent zlib windowBits handling from libpng-1.6.3beta06
[libpng17] Imported from libpng-1.7.0beta13.tar
[libpng17] Bump version to 1.7.0beta14