backward-compat aliases, in preparation for a subset of these flowers
being added to "common".

also default debug to false again

oversight in the engine that in turn revealed a bug in my code)

plants_lib/init.lua:83: bad argument #1 to 'getn' (table expected, got nil)

better way to set default biome params, optimized-out some copypasta, thanks
to thexyz for spotting these.

deleting nodes surrounding the spawn target during the mapgen code, replacing
the spawn target, and checking the type of node directly below the spawn
target.

every time an ABM or on_generated is called.  Optimized a number of nil
comparisons ("if x == nil" -> "if not x" and similar).

plants_lib's calls to do something extra when a tree is generated at mapgen
time or spawned via the growing code.

Thanks to paramat for spotting this!

copied and pasted directly into one's code).

to read and more clear on what stuff means.

in the spawning ABM after all other biome tests and general checks (aside from
spawning at the sides/bottom/top of a node) are done.

and to allow the spawned object to *replace* the node it would otherwise
spawn on top of.

Also, extended API to allow for a node to be directly named in the
register_generate_plant() call.

in the spawn_on_surfaces call actually work.  Fixed.

calling options.  This opens the door for even more features in the future.
Changed flowers, junglegrass, poisonivy to match.

Made plants lib faster in some places, especially the surface-hunting
algorithm, and especially over water.  Fixed a few other misc. bugs.

Made growth code properly execute all biome-control code before executing
any string-named function or spawn_tree().

Tuned flowers settings.  Made flowers require at least some light to spawn,
made waterlilies require shallower water.  Fixed a bug in water depth detection
and made water depth depend on whether the bottom of the water area is dirt,
dirt with grass, or sand, rather than just anything.

Made waterlilies randomly rotate on spawning to break up the patterns (now has
16 orientations with the help of nodeboxes and facedir, requires only 3 new
nodes). Smoothed edges of the regular waterlily texture.  Made all flowers and
water- lilies spawn using only 3 ABM calls instead of 8.

Got rid of colon prefix node def overrides on all plants, since this is a
modpack now instead of an integrated mod.  Fixed a misspelled folder name for
poisonivy.

Fixed a bug in the wall detection routine - it returned the last wall found,
not the first.

Made the top-side-check for air only apply when spawning on top of the
target rather than its sides/bottom.

Many other features and enhancements have been made.  Too many to list here.
Please see API.txt for details.

thanks to bas080 for spotting that one.

This causes trees to be just a tad more sparse than intended, but greatly
speeds up the map generator.

Worst case drops from thousands of nodes to test per tree type to a 5-15 nodes
per tree type.

under the plant to be grown and to check for air above it.