KDevPlatform Itemrepository bucket freeItems

[David Nolden]

For the item-repository, there is probably nothing reusable, because
the structure is embedded in a disk-mapped flat memory area, and each
single byte counts. The needs are very special. However, these trees
need to be implemented in a way that the code does _not_ become more
complicated than it already is, maybe by putting them into another
header. Also, it needs to be extensively unit-tested. Right now the
item-repository is very stable, and we can not risk this stability
just for a _small_ _potential_ performance boost.

Greetings, David