osutil.c: use readdir instead of readdir64 Some systems (e.g. *BSD) don't have a readdir64 function - the regular readdir already uses 64-bit types. On other systems (Linux, Solaris, ...), if Python was compiled with large file support, Python.h will define _LARGEFILE_SOURCE and _FILE_OFFSET_BITS=64, so that any call to readdir will actually be a call to readdir64. If Python was not compiled with large file support, we probably don't want to define these macros to avoid ABI problems.