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

Add minetest.get_server_uptime() function to Lua API

Update lua_api.txt.

	These methods do not actually fail but instead clear the item stack
	and return false if a value like e.g. "" is passed.

Add missing documentation for 'register_biome' and
'clear_registered_biomes'.
Add documentation for 'nodeupdate_single'. 'nodeupdate'
is not yet documented due to a bug it causes.

Adds a flag to forceload_block which lets you turn off persistence for
that forceload.

Add 'core.LIGHT_MAX = 14' to builtin/game/constants.lua with the intention
to replace misplaced 'default.LIGHT_MAX = 14' in Minetest Game.
Add comment in light.h requiring the constant be changed in both places.
Add lighting bug warning to note in lua_api.txt.
There are hundreds of mod uses of 15 which causes a lighting bug.

Maximum is 14.
A value of 15 (reserved for direct sunlight) causes a lighting bug.

Inverts the given channels of the base image.
Mode may contain the characters "r", "g", "b", "a".
Only the channels that are mentioned in the mode string will be inverted.

In lua_api.txt, make clear that 'place on' and 'spawn by' can be lists.

Adds several new ways that the plantlike drawtype mesh can be changed.

This requires paramtype2 = "meshoptions" to be set in the node
definition. The drawtype for these nodes should be "plantlike".

These modifications are all done using param2. This field is now
a complex bitfield that allows some or more of the combinations to
be chosen, and the mesh draw code will choose the options based as
neeeded for each plantlike node.

bit layout:
bits 0, 1 and 2 (values 0x1 through 0x7) are for choosing the plant
mesh shape:
  0 - ordinary plantlike plant ("x" shaped)
  1 - ordinary plant, but rotated 45 degrees ("+" shaped)
  2 - a plant with 3 faces ("*" shaped)
  3 - a plant with 4 faces ("#" shaped)
  4 - a plant with 4 faces ("#" shaped, leaning outwards)
  5 through 7 are unused and reserved for future mesh shapes.

bit 3 (0x8) causes the plant to be randomly offset in the x,z
plane. The plant should fall within the 1x1x1 nodebox if regularly
sized.

bit 4 (0x10) causes the plant mesh to grow by sqrt(2), and will cause
the plant mesh to fill out 1x1x1, and appear slightly larger. Texture
makers will want to make their plant texture 23x16 pixels to have the
best visual fit in 1x1x1 size.

bit 5 (0x20) causes each face of the plant to have a slight negative
Y offset in position, descending up to 0.125 downwards into the node
below. Because this is per face, this causes the plant model to be
less symmetric.

bit 6 (0x40) through bit 7 (0x80) are unused and reserved for
future use.

!(https://youtu.be/qWuI664krsI)

'maxwear' has been deprecated for over 3 years
Add spaces around '=' nearby

Add an [opacity:<r> texture modifier. Makes the base image transparent according to the given ratio. r must be between 0 and 255. 0 means totally transparent. 255 means totally opaque. Useful for texture overlaying.

Combine texture_overrides.txt and sections of lua_api.txt

Recommend mod screenshot size in lua_api.txt
Adjust displayed screenshot size of texture packs
Document texture pack files in lua_api.txt

Use the setting "profiler.load" to enable profiling.
Other settings can be found in settingtypes.txt.

* /profiler print [filter] - report statistics to in-game console
* /profiler dump [filter] - report statistics to STDOUT and debug.txt
* /profiler save [format [filter]] - saves statistics to a file in your worldpath
	* txt (default) - same treetable format as used by the dump and print commands
	* csv - ready for spreadsheet import
	* json - useful for adhoc D3 visualizations
	* json_pretty - line wrapped and intended json for humans
	* lua - serialized lua table of the profile-data, for adhoc scripts
* /profiler reset - reset all gathered profile data.
	This can be helpful to discard of any startup measurements that often spike during loading or to get more useful min-values.

[filter] allows limiting the output of the data via substring/pattern matching against the modname.

Note: Serialized data structures might be subject to change with changed or added measurements.
	csv might be the most stable, due to flat structure.

Changes to the previous version include:

* Updated and extended API monitoring
* Correct calculation of average (mean) values (undistorted by idleness)
* Reduce instrumentation overhead.
* Fix crashes related to missing parameters for the future and occasional DIV/0's.
* Prevent issues caused by timetravel (overflow, timejump, NTP corrections)
* Prevent modname clashes with internal names.
* Measure each instrumentation individually and label based on registration order.
* Labeling of ABM's and LBM's for easier classification.
  Giving several ABM's or LBM's the same label will treat them as one.
  Missing labels will be autogenerated based on name or registration order.
* Configurable instrumentation and reporting. Skip e.g. builtin if you don't need it.
* Profile the profiler to measure instrumentation overhead.

Modifications by est31: grammar fixes in doc + error messages and
a little style fix, no functional change.

This commit refactors the majority of the Mapgen settings system.
- MapgenParams is now owned by MapSettingsManager, itself a part of ServerMap,
  instead of the EmergeManager.
- New Script API functions added:
    core.get_mapgen_setting
    core.get_mapgen_setting_noiseparams,
    core.set_mapgen_setting, and
    core.set_mapgen_setting_noiseparams.
- minetest.get/set_mapgen_params are deprecated by the above new functions.
- It is now possible to view and modify any arbitrary mapgen setting from a mod,
  rather than the base MapgenParams structure.
- MapgenSpecificParams has been removed.

Deprecate get_look / set_look pitch / yaw

This allows a nodedef to specify a fixed value for param2 to be
used for all normal placements.

There are several uses for this:

- nodes that require param2 to be set to a non-zero value for
  internal mod use. E.g. leafdecay could use this to detect that
  leaves are played by players.
- force wallmounted or facedir value at placement at placement

This overrides any player look direction or other on-the-fly
param2 setting during placement.