Custom (non-engine) field names of items and entities are allowed.
This is now documented in lua_api.txt. Field names beginning with
an underscore are now reserved for mod use, the engine must not
introduce any fields beginning with an underscore.

This reverts commit 93e3555e.

Now, the renamed forms of nodeupdate and nodeupdate_single are part of the official API.

As nodeupdate has been used by Minetest Game and in mods despite of not
being part of the official API, we ease the transition by still supporting
it for the 0.4.15 release. After the release, the two functions can be removed.

The removal will not violate the stability promise, as that promise only
includes the official and documented API.

Also, make some formerly global functions local. They most likely haven't
been used by mods, therefore they won't get stubs with deprecation warnings,
hard erroring directly.

Active objects that are attached to other objects are not safe
from deletion. As a result, the parent object may have a reference
to an id of a child's that no longer exists.

If at some point an attempt is made to manipulate the child,
enviromment->getActiveObject(child-id) returns NULL. Using the
NULL pointer causes the crash...

In preparation for nodeupdate being renamed and made official API
in future.

This is a slightly modified and cleaned up version of #3774 by RealBadAngel.
By sofar: Remove color change (just make it lighter) and some minor cleanups.

* Fixed tooltips not resizing with \n

* Fixed it for 1.8.4 too.

* Fixed not working with Freetype disabled.

* Modified it to use Zeno-'s solution.

The client would not compute the distance from the camera to
to a mapblock correctly. The result was that blocks that were in
view (i.e. not beyond the fog limit) would not be rendered.

With the improved distance computation, a range adjustment that
existed in clientiface.cpp is no longer required.

The problem was seen while using the mobf mod package.

The problem happens when the server serializes entity attachments.
Sometimes, such attachments no longer exist. The serialization code
skips those. However, the total number of attachments was serialized
earlier.  Therefore the client expects more than it gets, and logs a
serialization error.

Remove unnecessary code.
Use '/ 2.0f' because endoff is a float.

Add missing documentation.

To be identical to the lower half of the skybox sides.
Now needed as the skybox base is often seen due to increasingly vertical
mapgens.

Use unused range argument in 'isBlockInSight()' to limit mapblock sends
to a sphere of radius 'max block send distance'.

'endoff', the maximum diagonal of a mapblock, was incorrectly calculated.
Half this value for the centre point of the mapblock.

Original commit by t4im, rebased and developed by paramat.
Fix CONTENT_IGNORE being replaced by falling nodes or causing large
areas of sand to collapse into itself.
Format some conditional code for clarity.
Add and clarify some comments.

- interact
- shout
- privs
- basic_privs

This resolves washy font and incorrect mouse handling on Windows if
a screen with high DPI is used.

Replace parameters with the equivalent /Ox

* Separate optional from require dep's in main menu

* Simplify modmgr mod dependency listing code

PlayerSAO::disconnected() function was historical and remove the link between SAO and RemotePlayer session. With previous attributes linked to RemotePlayer saving was working. But now attributes are read from SAO not RemotePlayer and the current serialize function verify SAO exists to save the player attributes.

Because PlayerSAO::disconnected marks playersao for removal, only mark playerSAO for removal and let PlayerSAO::removingFromEnvironment do the correct saving behaviour and all the disconnection process instead of doing a partial removal and let the server loop doing the RemotePlayer cleanup and remove some saved attributes...

Fix for previous commit.

Add minetest.get_server_uptime() function to Lua API

Update lua_api.txt.

* Create UnitSAO, a common part between PlayerSAO & LuaEntitySAO
* Move breath to PlayerSAO & LocalPlayer
* Migrate m_yaw from (Remote)Player & LuaEntitySAO to UnitSAO
* Migrate m_yaw from Player to LocalPlayer for client
* Move some functions outside of player class to PlayerSAO/RemotePlayer or LocalPlayer depending on which class needs it
* Move pitch to LocalPlayer & PlayerSAO
* Move m_position from Player to LocalPlayer
* Move camera_barely_in_ceiling to LocalPlayer as it's used only there
* use PlayerSAO::m_base_position for Server side positions
* remove a unused variable
* ServerActiveObject::setPos now uses const ref
* use ServerEnv::loadPlayer unconditionnaly as it creates RemotePlayer only if it's not already loaded
* Move hp from Player to LocalPlayer
* Move m_hp from LuaEntitySAO to UnitSAO
* Use m_hp from PlayerSAO/UnitSAO instead of RemotePlayer

When rewriting keycode.cpp I overlooked this function, fixes #4683 completely

this should fix #4683