sequ overload with start point

[vlazzarini]

This PR introduces a new version of sequ with a start point

kres = sequ(kstart, irhythm[], iinstr[], idata[], kbpm, klen [, kmode] [, kstep] \
            [, kreset] [, kverbose])
kres = sequ(kstart, irhythm[], iinstr[], idata[][], kbpm, klen [, kmode] [, kstep] \
            [, kreset] [, kverbose])

closes #2200

[vlazzarini]

man page edit will follow PR merging.

[rorywalsh]

I'm just wondering if this shouldn't be added as a new sequ2 opcode rather than overloading the existing one?

[vlazzarini]

I prefer not to proliferate the number of opcodes, since now we have the overloading mechanism in place.

[rorywalsh]

My first thought was a version 2 (which I have never liked), simply because that falls in line with how things have been done in the past and for better or worse has been a pretty consistant approach.

[vlazzarini]

I see, but we did not have a consistent overloading mechanism back then, now we do, so I thought we may as well promote it.

[rorywalsh]

I wonder if we might now go back and overload all those other version 2 opcodes, marking them as deprecated. There was also talk of moving toward a consistent naming pattern for all opcodes. This is probably part of a larger discussion, but consistency leads to clarity. Anyhow, this PR is merged now. We can take up this discussion in another thread. 👍

[vlazzarini]

I think that is a good idea to explore.