Committed verbatim.

Accepted and assigned back to Trent.

I hate parts of this patch but can't think of anything substantially better without massive changes everywhere.  For example, testing whether SIZEOF_TIME_T > SIZEOF_LONG and then *assuming* LONG_LONG is long enough is the same kind of dubious assumption that broke on Win64.  The new dubious assumptions are likely to hold true for years to come, but it's still unprincipled.
Still, all in all, fixes a real problem now and a principled alternative is A Project.

Hmm.  Assigning back to Trent.  Could have sworn I did that the first time!

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This patch fixes the posix module for large file support mainly on Win64,
although some general cleanup is done as well.

The changes are:
- abstract stat->STAT, fstat->FSTAT, and struct stat->STRUCT_STAT
  This is because stat() etc. are not the correct functions to use on Win64
  (nor maybe on other platforms?, if not then it is now trivial to select the
  appropriate one). On Win64 the appropriate system functions are _stati64(),
  etc.
- add _pystat_fromstructstat(), it builds the return tuple for the fstat
  system call. This functionality was being duplicated. As well the
  construction of the tuple was modified to ensure no overflow of the time_t
  elements (sizeof(time_t) > sizeof(long) on Win64).
- add overflow protection for the return values of posix_spawnv and
  posix_spawnve
- use the proper 64-bit capable lseek() on Win64
- use intptr_t instead of long where appropriate from Win32/64 blocks
  (sizeof(void*) > sizeof(long) on Win64)

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