Optimise the fetching of global settings 'camera_smoothing',
'cinematic' and 'cinematic_camera_smoothing'.
Cache 'cam_smoothing'.

When loading a block add liquid-nodes that might flow away or spread to
neighbours to the transforming_liquid queue.

Prevent waterfalls from falling down or streams from flowing away when the
source node is in an unloaded block - Nodes near a CONTENT_IGNORE node will
be interpreted as if the ignored node is a liquid node that just supports
the current state of the nodes in question.

To avoid smaller biomes when extra biomes are added to MTGame.
The addition of bushes in MTGame grasslands makes wood resources easier
to find and less distant, so slightly larger biomes are now acceptable,
but also desirable to encourage travel and create more sense of adventure.

Fixes https://github.com/minetest/minetest/issues/4832

Floatland base terrain underside was too thin, causing excessive water
leakage through tunnels under lakes, now make it thicker.
Floatland mountain terrain had a rim 1 node thick which made it bare
stone, now make it 2 nodes thick to merge with the floatland base
terrain rim and to have a layer of biome material.
Make mountain terrain more exponentially shaped by altering the
exponent.
Remove unnecessary and potentially ugly MYMAX() applied to
n_base_height.

Optimize/adjust blocks and active blocks sent at the server based on client settings.

This combats the problem of sending the hundreds of
"creative" / "armor" or whatever detached invs that
exist on popular servers to each and every player
on join or on change of said invs.

Since light_source>15 causes crash, it must be limited.

(was broken by e4ee6548)

Previously, paths like ./worlds would be resolved to /worlds since the
leading dot was considered just as irrelevant as a dot in the middle of
the path.

It used to drop all of the return values from the
insecure version of the function.

This will only happen if the formname matches or if formname is "".

This merge doesn't make any functional changes. It's a trivial style fix so that @gregorycu can be dual credited along with shadowninja for PR #4800

This improves rendering performance by ~40%

Position, velocity and acceleration vectors of particles are rotated
by the yaw of the parent object so that they are truly relative to it.
Clarify new attached particle spawner behavior in lua_api.txt.

If a tool wears out and is destroyed, it's itemstack count
goes to 0, and we can optionally play a breaking sound.

This patch implements playing a breaking sound when this
occurs. Sounds need to be added to the tool itemdef
registration as the sound name string in the .sound.breaks
member.

Fixes #4778 which was about the error:

ServerError: Lua: Runtime error from mod '' in callback item_OnPlace():
/usr/local/share/minetest/builtin/game/item.lua:278: attempt to call global 'check_attached_node' (a nil value)

The issue was a regression of commit 649448a2

"Rename nodeupdate and nodeupdate_single and make them part of the official API"

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.