in favor of more normal "." notation.
In the process, I have renamed a few functions in favor of
more meaningful names (see API.txt), and provided
"compatibility shims" for old mods where needed, with warnings.
since nothing much is normally found outside that range anyway
only enqueue blocks that are within that range, or within
the range specfied by all of the mods that make generate_plant() calls,
whichever covers more volume.
