Near:
    - Check the outputs for proper wrap use.  eg GsfOutputGzip does not
    - Complete MS property set read and write
      (complete codepage support for writing)
    - work on GsfOutput error handling to propagate errors up the stack.
      Maybe something signal based ?
    - for the stdio output check that we can actually write to the target file
      on open even though we do not want to write to it until later.
    - Add 'cancel' flag to GsfOutputStdio to support not overwriting the target
      file even if things succeed.
    - sync ODF document-statistic with OLE2's document-parts and various counts

Longer:
    - More work on VBA directory parsing so that we can decompress
      source streams.
    - Add encrypt and decrypt wrappers
	- precede with some randomness due to static nature of xml header
	- be absolutely clear about how we handle seek (only encrypt data on
	  first pass)
    - Can we do we put a mechanism for signing and authenticating ?

Future:
    - parse vba p-code directly to produce some other language.
    - move biff utils here from gnumeric

------------------------------------------------------------------------------------
potential 2.0 api changes

- Infile::get_child*  To take a GError to handle failure
- Convert Input, Infile, Output, Outfile into interfaces
- Split Input/Output into base and seekable
- Remove/Alleviate requirement that we know the size of a stream on open
- input::seek and output::seek use the opposite conventions