It returns the index used in mg->biomemap for a given biome name.
The biomemap is useless without this unless you re-register all existing biomes,
which could cause problems for anyone else trying to use biomemap.
With this, you can quickly create a lookup table of ids and names.

Because not all circles are round:
* circles using an euclidean metric are what we usually call "round"
* circles using a maximum metric look like euclidean rectangles with equal adjacent sides (squares)
* circles using a manhattan metric look like an euclidean right angled rhombus (squares, but 45° rotated to the former one)

[ci skip]

Thanks to @kaadmy (NeD) for pointing this out.

Document the node metadata changes of the commit (serialisation version >=23):

704782c9 "WIP node metadata, node timers"

Fix regression since commit:

915807f8 "Rename doc/mapformat.txt and update doc to match SRP changes"

And add an underscore to doc file name to make it more readable.

1. Do two renames:
	* SER_FMT_CLIENT_VER_LOWEST -> SER_FMT_VER_LOWEST_WRITE
	* SER_FMT_VER_LOWEST -> SER_FMT_VER_LOWEST_READ
Now the two define values are consistently named with the _WRITE defines
SER_FMT_VER_{HIGHEST,LOWEST}_WRITE, and to better point out what the two
serialisation versions actually are for.

2. wrap some lines in doc/worldformat.txt, and point out that the node
timers are serialized at a later point, as this can cause confusion about
what now happens (if one doesn't strictly read the if block's conditions).

3. some whitespace fixes in NodeTimerList::serialize, and one new comment.

The documentation file contains not just information about the
map itself, but also about further files inside the world's
directory.

Documentation didn't reflect recent SRP addition, now it does.

Modders are now able to select the range of ore column height,
and the midpoint at which they 'grow' starting from.
This commit adds three new parameters for the 'sheet' ore type:
column_height_min, column_height_max, and column_midpoint_factor.
clust_size is now deprecated for this ore type.

Enable the server to request the client to reconnect.

This can be done with the now extended minetest.request_shutdown([reason], [reconnect]) setting.

The neighbours checked are the 8 nodes horizontally surrounding the decoration base
and the 8 nodes horizontally surrounding the ground node below the decoration

Adds list-rings, a method to implement item sending between inventories via shift-click.
Nice insider feature: a ring consisting of a single inventory list serves as nice clean-up method.
Also adds them to minimal game, and the standard inventory.
Craft output slots are not supported.

ObjectRef:
get_properties
get_armor_groups
get_animation
get_attach
get_bone_position

Players:
get_physics_override
hud_get_hotbar_itemcount
hud_get_hotbar_image
hud_get_hotbar_selected_image
get_sky
get_day_night_ratio
get_local_animation
get_eye_offset

Global:
minetest.get_gen_notify
minetest.get_noiseparams

This adds the ability to grab 'slices' of noise calculated by PerlinNoiseMap.
Retrieving smaller slices of noise from the computation result as needed
optimizes memory usage while maintaining a reasonable amount of CPU overhead.