overall performance (was: skyline performance)

[Graham Percival]

Han-Wen Nienhuys wrote:
> I've just pushed a change which enables (commented out) skylines for
> separation items. Could you have another look at skyline performance?
> I'm seeing a signifcant performance impact on enabling it.

Would it be desirable to have
\fastProcessing
\qualityProcessing

macros?  I'm thinking of things such as
\override Score.PaperColumn #'keep-inside-line = ##t

Skyline processing would be another candidate for such commands if it 
could be easily turned on and off.  In the early stages of typesetting 
(getting pitches and rhythms correct), nobody cares about collisions or 
good page turns or whatever, but in the latter stages these becomes 
critical.

Cheers,
- Graham