use minetest.override_item() instead

If moretrees is not present, nature_classic spawns blossoms and
eventually apples on default trees, as it always has.

If moretrees IS present, the code will only spawn apple blossoms on
moretrees' own apple tree leaves, and will only grow new apples on those
trees, not on default trees.  In this case, the nature:blossom node is
considered deprecated and is aliased to default:leaves to avoid causing
undefined nodes in old maps.

The fruitless bush isn't an independent item, but a node type used only
for its appearance, representing the the fruitless state of some specific
type of fruit bush.  One should never have a fruitless bush in inventory,
and it makes no sense to plant a fruitless bush per se.

blossoms/apple spawning portion only
does not include the iron trees or tree-growing code as those are obsolete

thanks for catching that, Gael de Sailly!

phase out the old hand-rolled protection function
drops support for old protection mods

Should also be faster...

DEPRECATED:  Don't use strings to pass function names to the mapgen code,
use an actual function call i.e. my_code(pos) instead.

Specifically, override the unattractive ones from that mod with the ones
from this, instead of having two kinds of strawberries, ugly and not
ugly.

cache type() check of node/function/model, always check if it's string
before trying to execute that string as a function.

Make sure that bad function calls fail safely, and failed function
calls don't leave spawned=true

left the actual function in, and replaced one call with a print statement
since if it happens, it indicates a non-fatal error that should always be
reported anyway (invalid object refs in mapgen calls)

in register_generate_plant() call (to handle e.g. unknown nodes being spawned)

I fear the dbg

gt