Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r258904, r259780:
Small ext2fs updates.

Add two new reserved inodes.
Make the hashing algorithm match the linux code.

PR: kern/183230

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Small typo.

MFC after: 3 days

Add license for the half MD4 algorithm used in ext2_half_md4().

The htree implementation uses code derived from the
RSA Data Security, Inc. MD4 Message-Digest Algorithm.

Add a proper licensing statement for the code and clarify
the corresponding comments.

Approved by: core (hrs)

Initial implementation of the HTree directory index.

This is a port of NetBSD's GSoC 2012 Ext3 HTree directory indexing
by Vyacheslav Matyushin. It was cleaned up and enhanced for FreeBSD
by Zheng Liu (lz@).

This is an excellent example of work shared among different projects:
Vyacheslav was able to look at an early prototype from Zheng Liu who
was also able to check the code from Haiku (with permission).

As in linux, the feature is not available by default and must be
enabled explicitly with tune2fs. We still do not support the
workarounds required in readdir for NFS.

Submitted by: Zheng Liu
Tested by: Mike Ma
Sponsored by: Google Inc.
MFC after: 1 week