Do not use syscall.Stat_t on Windows.
Drop the compile tag from the windows version (the file name covers it).
Simplify.
Merge pull request #1284 from ericsnowcurrently/backups-syscall-windows

Use syscall.Stat_t only on non-Windows.



(Review request: http://reviews.vapour.ws/r/599/)
Do not use syscall in tests.
Merge pull request #1285 from ericsnowcurrently/backups-syscall-test

Do not use syscall in backups tests.



(Review request: http://reviews.vapour.ws/r/600/)
Fixes for environs