Rework the function and local names section.

[ghost]

A proposal to address:

1. The naming of the imports.
2. Deal with duplicate names by design, by defining them to be prefixes. The runtime would be expected to add a unique suffix to resolve duplicates, and this might be taken advantage of by the producer to reduce the compressed size.
3. Allow zero length names to support the use case of the file size increasing more gracefully as names are added. This property depends on blocks of zero compressing well.
4. Move the name length first to help address the use case of having a directory to lookup the name strings.
5. Split function names and local names into two section. Seems to be a better fit to an 'extension' model. E.g. A runtime could ignore the local but still name functions. If other names are added in future they can go in additional sections without breaking the existing name sections.