Fix slabs combining into a cube: Facedir is only set for the cube if it has
paramtype2 = "facedir". This avoids liquid appearing in connected
framed glasslike.

All stair/slab nodes with parent nodes that are rotatable (wood and bricks)
are reverted to not having world-aligned textures, to fix the breakage of
rotated stair/slab appearence in worlds.

Update, and add missing documentation to, game_api.txt.

Before, it checked if the node name *contained* "stairs:slab_", which could detect
things like "xxxxxstairs:slab_xxxx". Changed the pattern to "^stairs:slab_".

Unbind table groups for base block, stairs, slabs.

Fix 'stair_images' code to avoid 'stair_images' being empty in some
situations.
Change stairs back to nodeboxes to make world-aligned textures work.

Original recording by Ryding.
http://freesound.org/people/Ryding/
Found by Anth0rx, edited by paramat.

Add and use 'default.node_sound_snow_defaults()' function.

With thanks to MarkuBu for the original PR and GreenXenith for the stair models.

If backface culling is not specified for a tile in 'images' it is set to true.
Slabs already have backface culling due to being defined as nodeboxes (which
are then converted to meshnodes).

No longer have 2 recipes for stairs, choose the one that matches the appearence
in inventory (stair rising toward the right).
Helps to reduce recipe count now that an increasing number of stairs are
being registered.

Slabs are placed horizontal instead of vertical, even if they are
placed on a wall.
Slabs are rotated automatically if they are placed to another slab,
no matter which material.
Slabs are placed at the lower position if the placer points into
the lower half of the pointed node and to the upper position if
pointed to the upper half.
Stairs are placed normal if the placer points to the lower half of
the pointed node and rotated upside down if pointed to the upper half.

Add desert and silver sand-related blocks, and stairs.

Edited fuels: fences, wooden ladder.
New fuels:
boat, paper, book, dry shrub, stick, vessels shelf, wooden tools,
wooden door, trapdoor, fence gates, farming crops, stairs, slabs, beds.

Combine slabs if identical based on orientations using a simple lookup
table if the nodes are identical.

Otherwise relies on place_node() to place the node, which properly
handles rotation compared to adjacent nodes already, and can orient
based on look_dir as well.

Initial slabs placed are oriented based on (1) the orientation of
the pointed "face" (assumes nodes are cubic, of course), and uses
the player look direction to orient the node n/e/w/s if the slab
is horizontal or upside-down. If placed against a vertical face,
the slab is placed against the face without rotation around the axis
perpendicular to that vertical face. This allows upside down placement
and vertical placement without screwdriver.

If a slab is placed on top of an upside down slab, or below a normally
placed slab, the rotation is inverted so that no "floating" slab
is created.

Largely based on kilbith's #807 PR. Slab combining and place_node()
usage by sofar.

Since this relies entirely on `on_place` mechanics, this fails to
combine slabs into a plain node if the space *above* is occupied.
This is unavoidable due to the fact that on_place() happens after
the checks required to see if pointed_thing.above is empty or not.

Make the softer woods, pine and aspen, 'flammable = 3'.
Correct inconsistent flammability of wood and stairs in relation
to all other solid wood nodes in MTGame.
Make the the softer woods, pine and aspen, 'choppy = 3'.

Useful for searches and the mod profiler.

Improve registration format
Fix groups not matching corresponding full node
Improve some descriptions

Make it consistent with the slab recipe which conserves volume

Allow water to turn cobble slab and stairs to turn into mossy versions.

There is no crafting recipe for mossy stairs and mossy slabs, the
stair/slab API has been modified to allow for a recipeitem that
is `nil`, which will omit adding a crafting recipe for these two
items. The API documentation is updated.

The slabs and stairs will turn mossy when water is adjacent, just like
cobblestone. You can either farm mossy versions by placing them in
water for a while, then collecting them, or run water over your craft.

Sandstone is crumbly = 1 cracky = 3 to be slowly diggable by hand
Sandstonebrick(stair/slab) is cracky = 2

Spread ABM intervals evenly across 1 to 16 seconds
16s ensures no nodes are missed when player walks past
Adjust chance values to compensate, for identical action rates
Combine lavacooling ABMs into one, return to chance = 1
Grass growth: add 'neighbors = "air"' to avoid
processing the thousands of underground dirt nodes
Grass death: Reduce action rate to that of grass growth
Fire: Use chance = 1 for flame extinguishing
and flame removal when mod is disabled

Organizing these in groups will allow mods to do several things
easier:

- create craft recipes using them as ingredients
- manipulate map nodes based on group properties

There are quite a few slab and stair blocks already, so automatically
add these groups at registration time for all of those. Since most
mods I've seen use the registration code in this submod, they will
also benefit.