[master] Removed test for PNG_CONFIGURE_LIBPNG from pngconf.h

pngconf.h

@@ -1545,7 +1545,6 @@ typedef z_stream FAR *  png_zstreamp;
 #      define PNG_ALLOCATED  __attribute__((__malloc__))
 #    endif
 
-#  ifndef PNG_CONFIGURE_LIBPNG
     /* This specifically protects structure members that should only be
      * accessed from within the library, therefore should be empty during
      * a library build.
@@ -1564,9 +1563,8 @@ typedef z_stream FAR *  png_zstreamp;
 #        define PNG_PRIVATE \
           __attribute__((__deprecated__))
 #      endif
-#    endif
-#  endif
-#endif
+#    endif /* PNG_PRIVATE */
+#  endif /* __GNUC__ */
 #endif /* PNG_PEDANTIC_WARNINGS */
 
 #ifndef PNG_DEPRECATED