Bulk-loading results in invalid trees

[db7]

Often, bulk-loading a tree results in trees with more children than MaxChildren and more levels than returned by Rtree.Depth(). The searches seem to be unaffected, but that may cause issues when inserting or deleting entries after bulk load.

There are several issues in the OMT bulk-load implementation that cause the invalid trees:

• the calculated height by the algorithm does not match the depth reached during recursion
• the splitting of vertical slices results in not fully packed leaves
• the same problem results in non-leaf nodes containing more children than MaxChildren

We found this problem while trying to reduce the allocations in the KNN search, see issue #24.

[dhconnelly]

Assuming your pull request fixed this. Thanks for the contribution!