Merge remote-tracking branch 'srht/master'
Store children quadtrees in an array instead of as slots.
Added some benchmark functions.

Also added inline and optimization declarations.
Add point-quadtree png visualization, fix pr-quadtree insert.
Add parametric-animation function.  Tweaks to parametric-quadtree.
Fix bug in split-quadtree, enhance view-quadtree, add parametric-quadtree function.
Implement view-quadtree and range-find for pr-quadtree.
Move entries out of quadtree.

Subclasses are now responsible for storing data.
Fix tests.

Made the tests pass when they catch a not-impemented error, so that they start
failing if the methods are implemented.
Remove indentation on empty line.
Insert into pr-quadtree is now working.
WIP: Work on pr-quadtree insert and split-quadtree.
Fix point-quadtree range-find.
Big refactor and cleanup before adding pr-quadtree.
Rename entry to entries in quadtree and change type.

Allows subclasses to treat entries as a single entry or a list of entries.
This will allow future optimizations where multiple entries are stored in the
same quadtree-node prior to subdividing.
Add quadtree-entry to hold point and data.

Refactored point-quadtree to use quadtree-entry.
Small refactor of range-find for point-quadtree.
Add errors for methods that aren't implemented.
Merge branch 'master' of git.sr.ht:~jl2/quadtree