Merge branch 'topic/wysh'

Merge branch 'topic/wysh'

* topic/wysh:
  nail.1: add note to quote ; and | (hopefully we get there!)
  Drop list.c, add new cmd_arg.c..
  n_shell_quote(): rewrite, tweak user-at-a-glance experience
  MLE: change HT expansion..
  Drop wordexp(3), instead unroll via fnmatch(3)..
  Localize n_shell_expand_tilde() and n_shell_expand_var()..
  Add n_shell_parse_token_buf() wrapper
  n_shell_quote*(): add a "roundtrip" argument
  Add n_visual_info(), drop field_detect_width()
  n_shell_parse_token(): correct handling of comments
  Sprinkle #ifdef HAVE_NATCH_CHAR; ensure \x/\u doesn't clash data..
  Add n_iconv_onetime_cp()..
  `remove': use sh(1)ell-style quoting
  Drop fexpand_nshell_quote(), all users go for sh(1)ell-style
  (BWDIC!) Only use new sh(1)-style quoting for `write'
  Remove n_shell_sep() again, instead _pimp_ n_shell_parse_token()!
  Remove n_strescsep() again..
  (BWDIC!) Only use new sh(1)-style quoting for attachments!
  (TMP) Add n_shell_sep(), a better successor of strsep()
  (TMP) wordexp(3) or nothing, no longer use 'echo %s' for expansions..
  Add FEXP_NVAR (do not even expand $VAR)
  `customhdr': disallow using control characters in bodies
  Add PS_WYSHLIST_SAW_CONTROL and auto-check for control characters
  Only support sh(1)-style quoting for some new commands..
  Support `wysh' keyword prefix, here and there
  Introduce `wysh' command prefix to change argument parser..