Don't use TOSERVER_RECEIVED_MEDIA but TOSERVER_CLIENT_READY as indicatio for client ready
Handle clients with protocol version < 23 (almost) same way as before
Make client tell server about it's version
Add client state to not send bogus player position updates prior init complete
Add access to statistics information (peer connction time,rtt,version)
Fix clients standing stalled in world while preloading item visuals (new clients only)
Add get_player_information to read client specific information from lua

Parallax mapping with slope information.
Overriding normal maps.

Add check for datatype overflows
use native datatype indices instead of fixed 16bit/32bit ones

Use tables for adding particles, deprecate former way.

separate particles(pawner) definition, add default values, work with no
arguments

This doubles performance on some window managers (WTF?!)

Move most of the media-related code in client.cpp into a new class
ClientMediaDownloader (clientmedia.cpp, clientmedia.h). Among other
things, this class does the following things:

- Download [remote_server][sha1] instead of [remote_server][name]. This
is to support servers that provide the same file name with different
contents.
- Initially fetch [remote_server]index.mth. This file should follow the
Minetest Hashset format (currently version 1) and contain a list of SHA1
hashes that exist on the server.
- The list of needed SHA1s is uploaded (via HTTP POST) when index.mth is
requested, so servers can optionally narrow down the list to the needs
of the client.
- If index.mth is missing (HTTP response code 404), we enter compat mode,
fetching [remote_server][name] as before this commit.
- remote_server can now contain multiple servers, separated by commas.
The downloader code attempts to split requests between the different
servers, as permitted by each server's index.mth. If one server claims
to have a file but actually doesn't (or something fails), we ask a
different server that also claims to have it.
- As before, when none of the remote servers provide a particular
file, we download it via the conventional method, i.e. using
the minetest protocol: TOSERVER_REQUEST_MEDIA / TOCLIENT_MEDIA.
- Bugfix: Every downloaded file's SHA1 is now verified against the SHA1
announced by the minetest server (before loading it and inserting it
into the file cache).
- Bugfix: Only send TOSERVER_RECEIVED_MEDIA when we actually have all
media. This should fix #863.

Texture names must now be escaped in formspec elements image[],
background[], image_button[], image_button_exit[].

Instead of special-case handling of texture loading (and unloading
which was missing) in guiFormSpecMenu.cpp, use the newly created
ISimpleTextureSource interface which is a minimal subset of
ITextureSource. There is an implementation of this interface
used by GUIEngine (MenuTextureSource).

Fix an off-by-one bug in unescape_string; it caused requests for a
texture called "\0".