Blender Git Loki

Fix T51774: Children particles hair interpolation not correct with textures or dp.

Children where always getting at least one segment of fixed length...

Now fully hidden ones (zero length) get no segment at all.

Note that even very short ones keep getting one 'unit' length segment - would
rather avoid changing that at this point, given how complex children
particles 'length' can get with all kind of modifiers... Think we can
live with that for now anyway.

Add Cone: tip soft-min should be zero

Default value should be included in range.

Add same new ID freeing API as copying one.

Idea is the same, looks like it will be a tad simpler than with copy
though, since we should not need to change each ID type freeing func, as
ID usercount handling is done in main BKE_library code (would like to do
that for copy as well, but it's not that simple).

Fleshing a bit new copy logic (using Object datablock as Guinea pig).

Layout initial ideas/code structure of new ID copying.

On second thought, avoid adding new stuff to ID.

We can extend ID->tag and store there our few alloc-related tags.