Portals will now fail to ignite instead of defaulting to a fallback depth of (starty - 256) when no unprotected target can be found.
The search depth is also increased from (starty - 256) to (starty - 646)
This is to properly handle large protected areas that are sometimes set up at spawn - see issue #26
* respect protected areas when spawning remote portals
* Use portal_shape to determine area to check for natural/protected
* Log warning on deprecated function call
(new animation by Extex101)
The original texture is now "nether_portal_alt.png", and used to provide a "nether:portal_alt" node, which is used/demoed by the Surface-portal as the original animation still has a "it's full of stars" charm coming out when used for lighter coloured portals.
Improvements found while using the portals API in another mod (cloudlands):
* remote_portal_checkup() will check the whole portal and frame for mapgen overwrites.
* Allow find_realm_anchorPos() to return nil if no realm location could be found (portal will fail to ignite).
* Allow create_book_of_portals() to be invoked [indirectly] by other mods.
Also lowers nether_book_close.png to be 4bpp
https://forum.minetest.net/viewtopic.php?t=15912
Don't place Book of Portals in dungeon chests if its contents can be written in the help modpack Encyclopedia instead, and don't add Book of Portals to dungeon chests if Nether portals are the only type of portal - A Nether mod doesn't need a Book of Portals if it's only being used to provide a Nether portal.
Also adds nether.register_wormhole_node(), moving the wormhole node template into portal_api.lua, and allowing wormhole nodes with custom post_effect_color to be more easily created.
UTF-8 with BOM crashes some systems according to 6551f5c120 comment, and there are several cases where Minetest is buggy with files that use CRLF line endings (though none I'm aware that affect these files), so strip CRs and BOM
This is effectively a missing part to the change that made locate_or_build_portal() enforce that portals only link together in mutual pairs. As target portals that didn't need to be located or built we not being updated to link back to where the player travelled from.
Also
* implements events: on_run_wormhole, on_extinguish
* adds a lot of debug info
