Optimisation

[yaxu]

Ref the discussion here:

https://club.tidalcycles.org/t/generalizing-swing-and-rotating-uneven-rhythms-by-mapping-integers-from-a-latent-space-to-time/

#1078 Improves the efficiency of sew and it's dependents e.g. while considerably, by only querying the source patterns twice, rather than for every event in the boolean pattern.

stitch and probably other functions should get the same treatment