merge ac_lib_readline.m4 from microdc

* imv extresso.in ->
  imv: overwrite `extresso.in'? y
  mv: overwrite `extresso.in'? y
  Fix this by passing -f option to mv? Will this not interfere
  with other mv options?

* (dual-column) make option to control minimum accepted number of
  spaces between source and destination name.
  this will affect even when autowidth is enabled (in that case
  it would set the default number of spaces between names).

* (editing.c) if input fails, we're left in a bit unsure mode.
  what should we do?

* Verify multiple arguments with ls (after CHDIR changes)

* New option:
  -C, --confirm			ask if changes really are to be made
  (This is done before calling apply_plan)

* Maybe add `help' to format option help?

* Deal with more errors:
  wrong escape (\ ) sequences in format
  renaming dirs - rename no longer exists?
  permission in source directory
  permission to source file
  permission in destination directory
  permission to destination file
  ...

* Write replacement wordexp to handle "", wildcards and ~.

* Short-hand aliases for all edit-format options:
  w for width, etc.

---

After version 1.0:

* Include `dpat' and `spat' similar utilities?
  Include `rename' (perl) clone written in C?

* Rename utility:
  -w wildcard/glob pattern: two arguments: *.bar *.baz
  -r POSIX regular expression: single: s/(.*)\.bar$/$1\.baz/
  -t translate characters like perl tr//: "tr/abc/ABC/"
  -l lowercase all characters
  -u uppercase all characters
  -U[WORD-DELIM] uppercase first characters, lowercase rest

* Substitution renaming in qmv like perl rename(1)?
