sftp: add required packages to vendor

vendor/github.com/pkg/sftp/server_statvfs_impl.go

@@ -0,0 +1,25 @@
+// +build darwin linux,!gccgo
+
+// fill in statvfs structure with OS specific values
+// Statfs_t is different per-kernel, and only exists on some unixes (not Solaris for instance)
+
+package sftp
+
+import (
+	"syscall"
+)
+
+func (p sshFxpExtendedPacketStatVFS) respond(svr *Server) error {
+	stat := &syscall.Statfs_t{}
+	if err := syscall.Statfs(p.Path, stat); err != nil {
+		return svr.sendPacket(statusFromError(p, err))
+	}
+
+	retPkt, err := statvfsFromStatfst(stat)
+	if err != nil {
+		return svr.sendPacket(statusFromError(p, err))
+	}
+	retPkt.ID = p.ID
+
+	return svr.sendPacket(retPkt)
+}