Fix password hashing.

* Works (I hope) with $wgPasswordSalt set (default).
* Requires Digest::MD5 (core).

Signed-off-by: Xiong Changnian <xiong@cpan.org>
Merge branch 'feature-password' into devel

* Now creates hashed passwords that work onwiki.

Signed-off-by: Xiong Changnian <xiong@cpan.org>