Add a Microsoft port of dirent.h to support directory parsing
functionality. It is named windirent.h to avoid cases where the
compiler searches for headers in local directories first regardless
of chevron wrapping.

File source: https://github.com/tronkko/dirent
commit bf060f1569b156a6df15ea01ea0b4b5465243f06

Change-Id: I45bcf59883949a390b5471b62013a6d95d36903e
Tuleap: #799