This allows C-c : and C-u C-c : to work, modulo the printing of an
unnecessary [1]. The evaluation semantics of R are not what a Lisper might
expect; printToString(eval(parse(...))) does not necessarily perform the
evaluation before altering the output stream with sink() -- so capturing
all sorts of incidental output if something goes wrong.
This commit brought to you using C-c C-c.