CVS instability

[Jody Goldberg <jgoldberg home com>]

I have just committed a re-tooling of the style storage data
structures.  The result is significantly faster on large
spreadsheets.  There is still work to be done but this is an
important step in the right direction.  Michael's original interface
held up nicely so the changes for the rest of the system were fairly
minimal.

The code has been run through our standard tests and things seem
fine.  They've even been cleansed by Morten's mighty memory
methodologies.  Three things are known not to work :

    - only top & left borders will be drawn/printed
      The new scheme allows the age old cruftiness of borders to be
      fixed.  The style routine is ready, but the render does not
      use it.

    - Printing will stop at the bottom right cell with content,
      ignoring cells with visible styles father down.  This is a
      trivial patch.  Have a look at foreach_tile if interested.

    - The cell format dialog will not recognise all selected borders
      when it starts up.  This is an ugly problem that was
      originally solved with much work.  Sadly the new code can not
      directly use the previous implementation.

I'll finish up these loose ends shortly.

One final caveat :
Saving to xml still uses a scheme designed for the original style
engine.  It will work, but the results are likely to be more
fragmented than it needs to be.  It will also load more slowly than
the new engine allows.

I would recommend against using the CVS for production work.  Using
a microwave to dry your pet is also a bad idea.