This has to ensure that file names are unique among all files in an iso
directory. Current implementation can be improved by using a hash table
to keep the names, instead of iterate over all children. An alternative
method, keeping children sorted all the time, thus allowing binary
search, has been considered but discarded.
Current implementation support up to 9,999,999 equal files per
directory.
This only adds the tree creation functions, no sorting and name mangling
yet. Only plain ECMA-119 supported for now, nor RR, relaxed
restrictions, etc..
This also adds a little test program.
