Underscores in package names

To be clear, I'd be happy to contribute code to make this work, with
the changes mentioned by Duncan and elsewhere in the codebase, if
someone on R-core was interested in reviewing it.

You seem to have ignited a lot of discussion.

Just to add my own point of view:  I think removing a restriction on the 
allowed names is a generally bad idea.  I think Rasmus B??th gave a 
really valid complaint about the variety of naming conventions in R in a 
presentation I saw based on his article

https://journal.r-project.org/archive/2012/RJ-2012-018/index.html

Looking at the article now, it's not as entertaining as I remember his 
presentation was, but it makes good points about the value of consistency.

Duncan Murdoch