Enable FILE_SHARE_DELETE flag on Windows

[Jan Lehnardt]

Dear OTP Team,

the CouchDB team would like to propose the following patch to the
windows file driver:

  http://github.com/janl/otp/commit/01e91f903650454fecebf4ec8c8b5ee1f5b35253

It adds an additional flag to the CreateFile() syscall to allow multiple descriptors
to the same file to all request a deletion or rename of a file.

For more details, see "dwShareMode" on http://msdn.microsoft.com/en-us/library/aa363858(VS.85).aspx

Cheers
Jan
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