Auto merge of #620 - pornel:master, r=alexcrichton
Auto merge of #620 - pornel:master, r=alexcrichton

struct tm for Windows

As documented here:

https://msdn.microsoft.com/en-us/library/windows/hardware/ff567981(v=vs.85).aspx

I've verified it matches `corecrt_wtime.h` file from Win10 SDK.

rust-lang/libc,rust-lang-nursery/libc,rust-lang-nursery/libc,cactorium/libc,mneumann/libc,cactorium/libc,rust-lang-nursery/libc,rust-lang/libc,mneumann/libc,cactorium/libc,rust-lang/libc,mneumann/libc