[Rd] control list gotcha

[John C Nash]

This is mainly a reminder to others developing R packages to be careful not to supply
control list items that are not used by the called package. Optimx is a wrapper package
that aims to provide a common syntax to a number of existing optimization packages.
Recently in extending optimx package I inadvertently introduced a new control for optimx
which is NOT in any of the wrapped optimization packages. There are probably other methods
of keeping things tidy, but I copy the control list and null out unwanted elements for
each of the called packages. I missed this in a couple of places in the R-forge
development version of optimx (I'm working on fixing these, but they are still there at
the moment).

The "nasty" here was that the package mostly works, with plausible but not very good
results for some of the optimizers. If it crashed and burned, it would have been noticed
sooner. There is also a potential interaction with a use of the dot-dot-dot variable to
pass scaling information.

If there are ideas on how to quickly reveal errors related to calling sequences involving
control lists and "...", I'd welcome them (off-list?), and be prepared to summarize
findings in a vignette.

Best,

JN