[Rd] enabling core dumps

[pleydell at supagro.inra.fr]

To answer my own question.

My mistake was that "ulimit -c unlimited" applies to the current bash session
only. I had used this call in a bash *shell* buffer in emacs but this was
unable to affect R processes started in emacs with C-u M-x R, hence no core
files. Running the buggy code from R started in a bash shell after running
ulimit resulted in a core file being generated in the R working directory.

It's not the cleanest of emacs solutions, but at least it works.

David