Previous commits broke it... :(

Backface culling is enabled by default for all tiles, as this
is how the lua parser initializes each tiledef. We revert to
always using the value from the tiledef since it is always
read and serialized.

Mods that wish to enable culling for e.g. mesh nodes, now can
specify the following to enable backface culling:

    tiles = {{ name = "tex.png", backface_culling = true }},

Note the double '{' and use of 'name' key here! In the same
fashion, backface_culling can be disabled for any node now.

I've tested this against the new door models and this properly
allows me to disable culling per node. I've also tested this
against my crops mod which uses mesh nodes where culling needs
to be disabled, and tested also with plantlike drawtype nodes
where we want this to continue to be disabled.

No default setting has changed. The defaults are just migrated
from nodedef.cpp to c_content.cpp.

fixes minetest/minetest_game#786

cloneMesh() has to use a switch in order to create a different
mesh buffer type depending on vertex type. (Credit: the new cloneMesh
was written by RealBadAngel.)

To avoid repetitive code, all other methods use getVertexPitchFromType()
to automatically adapt the indexing to the vertex type at runtime.

Lua_api.txt: Document 'minetest.registered_biomes'
Minimal: Remove 'mapgen_air' alias
Cavegen: Add fallback node for 'mapgen_ice'
Dungeongen: Add fallback node for 'mapgen_river_water_source'
Mgv5: Remove unnecessary '#include util/directiontables.h'
Add missing 'this->'s in makeChunk()
Mgv6: Edit empty line formatting
Remove leading spaces in makeChunk()
Add missing spaces after 'for' and 'if'
Mgv7: Edit empty line formatting

The pageflip mode requires a stereo quadbuffer, and a modern graphic
card. Patch tested with NVidia 3D Vision.

The mini-map is not drawn, but that's what is done for topbottom and
sidebyside modes as well.

Also most of the time the user would prefer the HUD to be off. That's
for the user to decide though, and toggle it manually.

Finally, the interocular distance (aka eye separation) is twice as much
as the "3d_paralax_strength" settings. I find this a strange design
decision. I didn't want to chance this though, since it's how the other
3d modes interpret this settings.

Previously, we assumed that reply->str was NULL
terminated. However, this turned out to be not true,
as users reported crashes in strlen connected to
where reply->str was appended to an std::string.

Use the method recomended by the docs, to read the
length separately.

Add new node property 'floodable', default false
Define "air" as floodable = true in C++ and lua

Fix for commit 87dcee6a It uses the wrong variable and only covers some use cases. This change covers all use cases.

Removing the target file on other platforms was enabled likely unintentionally
by commit 5f1f1151.

This may be the reason why there has been corruption of files on Linux on hard
shutdowns.

Previously I described the problem and this fix in issue #3084.

My commit

e2d54c9f "shutdown when requested from lua in singleplayer too"

broke minetest's feature to connect to servers. The client crashed
after the connection init was complete.

Thanks to @sofar for reporting the bug.

Fixes #3498.

If an `XDG_CACHE_HOME` can't be found or `RUN_IN_PLACE` is enabled,
`path_cache` is left at its default of `$PATH_USER/cache`
(at a time when `PATH_USER` is `..`), rather than being reset to
`$PATH_USER/cache` after `PATH_USER` has been properly set.

And replace manual tests for error with SQLOK() where possible.

This allows other applications (e.g. minetestmapper) to interrogate
the database while minetest is running, without causing an almost
certain minetest crash.

This reverts commit f14e7bac.

Reverted due to missinterpretation of agreement, obvious dislike and me not interested in doing fights for feature I don't actually need

This reverts commit 91bafcee.

Reverted due to missinterpretation of agreement, obvious dislike and me not interested in doing fights for feature I don't actually need

Before, minetest.request_shutdown didn't shut down
singleplayer instances or server instances from the server tab.

This commit fixes this. Fixes #3489.

-> Redis backend: break from switch to fix bug
-> Dummy and redis backends: reserve the count so that creating the list is faster

Previous commit

70ea5d55 "Add support for limiting rotation of automatic face movement dir entitys"

by sapier has broken minetest's feature to open worlds. This was due to a
missing stack pop operation.

Thanks to @oleastre for reporting this bug and suggesting the fix.