[libpng16] Moved prototype for png_handle_unknown() in pngpriv.h outside of

the #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED/#endif block.
Removed recently-added #ifdef from pngpread.c; moving the prototype
in pngpriv.h fixed the compiler warning that the #ifdef was trying
to solve.

pngpread.c

@@ -537,10 +537,8 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
          png_push_save_buffer(png_ptr);
          return;
       }
-#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length,
          PNG_HANDLE_CHUNK_AS_DEFAULT);
-#endif
    }
 
    png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;