Revert "Don't leak textures all over the place"

This causes textures to be deleted before they are no longer accessed,
resulting in a segmentation fault. This needs to be rewritten in such a way
that textures are deleted when the client disconnects from a server.

This reverts commit 41c00e87d42580881d8c7001f39014814e3b55f2.
3D model support for players using Irrlicht. Also ready the basis for mesh support on nodes / items via LUA (to be done). Supports any mesh format compatible with Irrlicht, but animations are not set up yet.
Properly read the mesh from LUA.

Players can now be set to meshes using the following test script:

function switch_player_visual()
		prop = {
			mesh="player.obj",
			texture="player.png",
			visual="mesh",
		}
	for _, obj in pairs(minetest.get_connected_players()) do
		obj:set_properties(prop)
	end
	minetest.after(1.0, switch_player_visual)
end
minetest.after(1.0, switch_player_visual)
Fix material properties and allow lighting. Models should now be affected by light instead of being black
Add a subfolder for models and transfer models from server to client

(obj, md2 and md3 are currently allowed)

Get rid of the texture string and use the existing textures array. Segmented meshes have multiple materials, and this will allow us to texture each. Do not switch to this commit yet!

If a texture string is left empty in LUA, don't modify that material. Useful so a script can change specific textures without affecting others
Get the mesh working through the memory cache properly. Most credit goes to celeron55 for the help on this code

Get the texture from memory as well

Add .x to the list of supported formats

Update LUA API documentation
Allow the LUA API to set animations to meshes as well as the animation speed. Also update animations only when needed.

Support for animation blending, though for some reason it doesn't work.

Don't enable animation transitions by default for many reaosons

Object property to store individual bone positions. LUA can specify a bone name followed by a bone position. No functionality yet. Bone rotation to be added in the following commit

Same system for bone rotation, plus a few other things I missed
Joint positioning and rotation code, and fix a problem related to their lua API

Attempt to move the animation system to a more correct implementation, rather than using object properties. Incomplete and breaks functionality
Get the new animation framework properly working

Store start and end frames as v2f

Also move bone animations to their own function instead of object properties
Framework for the attachment system, new object property which allows changing the color and alpha of mesh materials

New object property which allows changing the color and alpha of mesh materials. Due to the current lighting systems it doesn't work yet, but the full implementation is there

Framework for the attachment system, with no actual functionality yet

Send bone and player object to the setAttachment function in content_sao.cpp, but we need a way to translate it there and send it to the client

I will also want position and rotation offsets to be possible to apply to attachments

Network object ID from server to client. This will be used to identify the parent client-side and know what to attach to
Complete the attachment framework.

The child ID can now be checked against the parent ID in content_cao.cpp so the parent can be detected. Actual attachment code to come

Divide attachment system between server attachments and client attachments, neither coded right now. As explained in the code comment:

// Attachments need to be handled on both the server and client.
// If we attach only on the server, models (which are client-side)
// can't be read so we don't know the origin and orientation of bones.
// If we attach only on the client, the real position of attachments is
// not updated and you can't click them for example.
Fix some remaining issues with attachments, now they work. Tested with object->player and player->player attachments
Enable client-side attachments, add detachment code
Send animations, bone overrides and attachments in entity initialization. Clients no longer have to be near an object when an animation or attachment is set to see the changes, and newly connected clients (or a client that simply renders the object for the first time) will get all of those settings. Therefore, the lua script no longer needs to run every X seconds either, just once per entity.

Finish fixing the material color code. But it won't work until MineTest has dynamic lighting... another day another feature.

Extra checks for the bone positioning / rotation code

Many checks and consistency improvements to the client attachment code

Make a separate function for checking if a client object is attached. A more in-depth change will be needed here to fix reading of invalid pointers

Use a different method of fetching the parent. Fixes the mass segmentation faults when rendering an attachment (some still happen though)

Major change to how attachments are handled. Fix the last segmentaton fault, which was due to the parent becoming invalid while being refreshed / removed which would bause the child to remain attached to nothing. Parents remove their children when being deleted themselves and add them back when re-added. Attachments are stored inside a 2D a vector which easily allows both a child to find their parent and a parent to find its children.

Remove attachment list entry when an object is being permanently removed. Also avoid duplicate entries in this list when re-attaching the same object

The "big code comments" can now go away. Client attachments almost work properly, and I know what else needs to be done
Update attachments at the ending of the addToScene function for parents. And with this... *drum roll* Client-side attachments are at last functional and stick visibly.

Fix the last segmentation fault (apparently). So far attachments seem to be fully functional, although removing the parent causes children to go to origin 0,0,0 and possibly still cause such a fault (though this should already be addressed)

Fix a bug in falling code where entities get stuck

Also check if the parent has been removed server-side, and detach the child if so. Fixes children going to origin 0,0,0 when their parent is removed.

Unset all attachment properties when permanently detaching (on both the client and server). Also store less data we don't need

Create a separate function for detaching, and also update lua api documentation

When a child is detached, update its position from the server to clients. This WILL cause it to get positioned slightly differently client side, as the server attachment system only copies parent origin and knows not about mesh / bone transformation. This prevents different clients seeing the object detached in different spots which is most correct

Update the position of attached players to clients. An attached player will see himself move, but this is currently VERY ugly and laggy as it is done by the server (it probably must stay this way too)

Use a different approach for locally attached players. This allows for smooth positio transitions to work, as well at the player turning around freely. Still buggy however
Fix more things I forgot for attached players. Such players will now properly see themselves moving when attached, and the server will read their position accordingly

Fix attached players being able to bob their view and generate foostep sounds by pressing a movement key (running in place)
Allow Vanessa's texture filtering / mipmap patch to work on models, as well as all other node types

Initialize m_bone_posrot too

Update pos_translator for attached players, which should fix a bug noticed with carts where a detached player would travel from the detachment spot to where it was detached

Don't make attachments possible to right-click either

Properly apply object and text visibility for local attachments, and fix them showing when they shouldn't
A bunch of fixes

No longer hide players who are dead. With models, a death animation should be used instead

Some changes requested by celeron55

Rename a lot of things in the code, and use better lua api function names

Minor code corrections

Bump protocol version up, since the models / animations / attachments code creates new client<->server messages
RealBadAngel's patch which allows the lua api to read pressed player keys. This should make it possible to change the player's animation based on what he is doing

Correct lua api version number

Always update animations and attachments after the entity is added to scene client side. Fixes animations not being applied in client initialization for some reason. Attachments should be re-tested now just to be safe.

Fix a segmentation fault caused by reaching materials that didn't exist in a loop for setting texture
Update ContentFeatures serialization format now as PROTOCOL_VERSION was changed