Log Message:
(devel/R-xfun) Updated 0.18 to 0.19

# CHANGES IN xfun VERSION 0.19

## NEW FEATURES

- Added functions `bg_process()` to run a command in a background
  process, and `proc_kill()` to kill a process.

- Added a function `del_empty_dir()` to delete a directory if it is
  empty.

- Added functions `is_abs_path()` and `is_rel_path()` to check if
  paths are absolute or relative.

- Added a function `is_sub_path()` to test if a path is under a
  directory.

- Added a function `is_web_path()` to test if a path is a web path
  that starts with `http://` or `https://` or `ftp://` or `ftps://`.

- Documented and exported the previously internal functions
  `dir_exists()` and `file_exists()` (thanks, @cderv, #36).

- Added a function `dir_create()` to create a directory recursively by
  default when it does not exist.

- Added an argument `fail` to `Rscript_call()` to allow users to
  customize the error message when an error occurred in calling the
  function in a new R session.

## MINOR CHANGES

- `file_ext()`, `sans_ext()`, and `with_ext()` no longer use
  `tools::file_ext()` or `tools::file_path_sans_ext()`, but provide a
  slightly different implementation. They treat `tar.(gz|bz2|xz)` and
  `nb.html` as file extensions, and also allow extensions to contain a
  trailing `~` or `#`.