Most keys are in form "<foo><bar>" where <foo> is either constant or one of very few choices.

This sucks when searching for a key because we need to compare several superfluous bits and the tree goes out of balance because many entries are alike.

So now we prepend key's checksum (in hex) to it. It makes the tree much more balanced (it's now only about two times as deep as optimal one would be) until I implement real balanced trees and it savessome character compares.