- manually inline mode_to_kind
- remove unused alloca include
- remove fstatat and associated bits
It's not obvious that there's an advantage to using fstatat in terms
of performance. The race-avoidance properties of fstatat aren't
terribly useful to us either. So best to avoid it until we figure out
how to use it portably.
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.
