Make std.file.setTimes safe

It contains the following unsafe operations but we can verify they can be trusted.

On Windows systems:
- use of `core.sys.windows.winodws.CreateFileW`, `CloseHandle` and `SetFileTime`
- use of `std.internal.cstring.tempCString` and `tempCString.Res.~this`
- (Fix) taking addresses of local variables (`ta` and `tm`)

On Posix systems:
- use of `core.sys.posix.sys.time.utimes`
- use of `std.internal.cstring.tempCString` and `tempCString.Res.~this`

Edit: I missed to wrap unsafe operations of taking addresses of local variables on Windows systems.
I fixed it.