fs: add support for FreeBSD

Change-Id: Ifb01913d17650e0fa729888f64cd2fe2017dfe1f

fs/dirstream_freebsd.go

+package fs
+
+// Like syscall.Dirent, but without the [256]byte name.
+type dirent struct {
+	Ino    uint64
+	Off    int64
+	Reclen uint16
+	Type   uint8
+	Pad0   uint8
+	Namlen uint16
+	Pad1   uint16
+	Name   [1]uint8 // align to 4 bytes for 32 bits.
+}

fs/files_freebsd.go

+package fs
+
+import "github.com/hanwen/go-fuse/v2/fuse"
+
+func setBlocks(out *fuse.Attr) {
+}

fs/loopback_freebsd.go

+package fs
+
+import (
+	"context"
+	"syscall"
+)
+
+var _ = (NodeGetxattrer)((*LoopbackNode)(nil))
+
+func (n *LoopbackNode) Getxattr(ctx context.Context, attr string, dest []byte) (uint32, syscall.Errno) {
+	return 0, syscall.ENOSYS
+}
+
+var _ = (NodeSetxattrer)((*LoopbackNode)(nil))
+
+func (n *LoopbackNode) Setxattr(ctx context.Context, attr string, data []byte, flags uint32) syscall.Errno {
+	return syscall.ENOSYS
+}
+
+var _ = (NodeRemovexattrer)((*LoopbackNode)(nil))
+
+func (n *LoopbackNode) Removexattr(ctx context.Context, attr string) syscall.Errno {
+	return syscall.ENOSYS
+}
+
+var _ = (NodeListxattrer)((*LoopbackNode)(nil))
+
+func (n *LoopbackNode) Listxattr(ctx context.Context, dest []byte) (uint32, syscall.Errno) {
+	return 0, syscall.ENOSYS
+}
+
+var _ = (NodeCopyFileRanger)((*LoopbackNode)(nil))
+
+func (n *LoopbackNode) CopyFileRange(ctx context.Context, fhIn FileHandle,
+	offIn uint64, out *Inode, fhOut FileHandle, offOut uint64,
+	len uint64, flags uint64) (uint32, syscall.Errno) {
+	return 0, syscall.ENOSYS
+}
+
+func intDev(dev uint32) uint64 {
+	return uint64(dev)
+}