[Backport #2416] win32's flock

Backport #2416: win32’s flock
http://redmine.ruby-lang.org/issues/show/2416

e$B5/I<<Te(B: Usaku NAKAMURA
e$B%9%F!<%?%9e(B: Assigned, e$BM%@hEYe(B: Normal
e$BC4Ev<Te(B: Yuki S.

[ruby-list:46578]
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