[ESS] Backslash at the end of R help command hangs ESS 5.3.1

[Richard M. Heiberger]

I also think it is a bug.  I tried the example.  Ctrl-G breaks
the frozenness, but still leaves me in an a loop of continuation
prompts.  I eventually got out of the loop by typing ")" and forcing
a syntax error.

The problem is that the key sequence "\[RET]" is interpreted as a character.
Usually it is the "\n" character.  in this setting it is something else
that I haven't spotted yet.

The fix for help is probably to adjust the expression
(defconst inferior-R-2-input-help (format "^ *\\? *%s" ess-help-arg-regexp))
on line 1616 of ess-inf.el.  I propose that Martin or Stephen take this on.

Rich