Windows: Native ANSI console support

Signed-off-by: John Howard <jhoward@microsoft.com>

system/syscall_windows.go

@@ -1,5 +1,34 @@
 package system
 
+import (
+	"fmt"
+	"syscall"
+)
+
+// OSVersion is a wrapper for Windows version information
+// https://msdn.microsoft.com/en-us/library/windows/desktop/ms724439(v=vs.85).aspx
+type OSVersion struct {
+	Version      uint32
+	MajorVersion uint8
+	MinorVersion uint8
+	Build        uint16
+}
+
+// GetOSVersion gets the operating system version on Windows. Note that
+// docker.exe must be manifested to get the correct version information.
+func GetOSVersion() (OSVersion, error) {
+	var err error
+	osv := OSVersion{}
+	osv.Version, err = syscall.GetVersion()
+	if err != nil {
+		return osv, fmt.Errorf("Failed to call GetVersion()")
+	}
+	osv.MajorVersion = uint8(osv.Version & 0xFF)
+	osv.MinorVersion = uint8(osv.Version >> 8 & 0xFF)
+	osv.Build = uint16(osv.Version >> 16)
+	return osv, nil
+}
+
 // Unmount is a platform-specific helper function to call
 // the unmount syscall. Not supported on Windows
 func Unmount(dest string) {