fix #17: proper embedded alignment of handleCounter

amd32 (raspberrypi) requires specific alignment for atomic operations to
work, or else you'll get "panic: runtime error: invalid memory address
or nil pointer dereference". Turns out this alignment is important for
embedded structs as well.
Embedding as the first member in the struct, and putting the atomic
field at the start of the embedded struct makes the alignment correct.

fscache.go

@@ -212,8 +212,8 @@ func (a *accessor) RemoveFile(key string) {
 }
 
 type cachedFile struct {
-	stream *stream.Stream
 	handleCounter
+	stream *stream.Stream
 }
 
 func (c *FSCache) newFile(name string) (fileStream, error) {
@@ -236,9 +236,9 @@ func (c *FSCache) oldFile(name string) fileStream {
 }
 
 type reloadedFile struct {
+	handleCounter
 	fs   FileSystem
 	name string
-	handleCounter
 	io.WriteCloser // nop Write & Close methods. will never be called.
 }