Percentage sign not escaped correctly inside backticks ``

[s-fleck]

The following code throws a warning and does not produce a valid Description under roxygen 6.0.1

#' foobar
#'
#' `0.5\%`
#'
#' @md
#' @export
foobar <- function(){
  NULL
}

The following produce a valid description, but not as wanted:

#' 0.5\%     works (but is not verbatim text)
#' `0.5\\%`  produces verbatim 0.5\%  (so no error, but an unwanted extra backslash)