Use Go 1.4 build environment (currently 1.4rc2)
Remove Windows specific implementation
Use same order of parameters as os.Symlink
Verify Windows support, report appropriate errors when unsupported
Merge pull request #1078 from syncthing/go1.4

Use Go 1.4 build env
Run filetype and symlink integration tests with versioning (ref #1071)
Handle broken symlinks, Simple versioner (fixes #1071)
Handle symlinks, Staggered versioner (fixes #1071)