Use completion-table-with-quoting for comint and pcomplete.

Use completion-table-with-quoting for comint and pcomplete.
* lisp/comint.el (comint--unquote&requote-argument)
(comint--unquote-argument, comint--requote-argument): New functions.
(comint--unquote&expand-filename, comint-unquote-filename): Obsolete.
(comint-quote-filename): Use regexp-opt-charset.
(comint--common-suffix, comint--common-quoted-suffix)
(comint--table-subvert): Remove.
(comint-unquote-function, comint-requote-function): New vars.
(comint--complete-file-name-data): Use them with
completion-table-with-quoting.
* lisp/pcmpl-unix.el (pcomplete/scp): Use completion-table-subvert.
* lisp/pcomplete.el (pcomplete-arg-quote-list)
(pcomplete-quote-arg-hook, pcomplete-quote-argument): Obsolete.
(pcomplete-unquote-argument-function): Default to non-nil.
(pcomplete-unquote-argument): Simplify.
(pcomplete--common-quoted-suffix): Remove.
(pcomplete-requote-argument-function): New var.
(pcomplete--common-suffix): New function.
(pcomplete-completions-at-point): Use completion-table-with-quoting
and completion-table-subvert.