sys/dev/xen/blkfront/blkfront.c:
	In xbd_thaw(), fix inverted logic to verify the queue is frozen
	before attempting a thaw.

MFC after:	1 week
Re-sort ext2fs headers to make things easier to find.

In the ext2fs driver we have a mixture of headers:

- The ext2_ prefixed headers have strong influence from NetBSD
and are carry specific ext2/3/4 information.
- The unprefixed headers are inspired on UFS and carry implementation
specific information.

Do some small adjustments so that the information is easier to
find coming from either UFS or the NetBSD implementation.

MFC after:	3 days