* lisp/progmodes/sh-script.el: Use post-self-insert-hook&electric-pair-mode.

* lisp/progmodes/sh-script.el: Use post-self-insert-hook&electric-pair-mode.
Provide SMIE-based indentation (not enabled by default yet).
(sh-mode-map): Don't bind electric keys.
Use electric-pair-mode instead of skeleton-pair.
(sh-assignment-regexp): Fit within 80 columns.
(sh-indent-supported): Specify actual shell name instead of boolean.
(sh--maybe-here-document): New fun, from sh-maybe-here-document.
(sh-maybe-here-document): Use it.  Make obsolete.
(sh-electric-here-document-mode) New minor mode.
(sh-mode): Use it.  Don't set sh-indent-supported-here here.
(sh-smie-sh-grammar, sh-smie--sh-operators, sh-smie--sh-operators-re)
(sh-smie--sh-operators-back-re, sh-indent-after-continuation)
(sh-smie-rc-grammar, sh-use-smie): New vars.
(sh-smie--keyword-p, sh-smie--newline-semi-p, sh-smie--sh-keyword-p)
(sh-smie-sh-forward-token, sh-smie--looking-back-at-continuation-p)
(sh-smie-sh-backward-token, sh-smie--continuation-start-indent)
(sh-smie-sh-rules, sh-smie-rc-rules, sh-smie--sh-keyword-in-p)
(sh-smie--rc-after-special-arg-p, sh-smie-rc-backward-token)
(sh-smie-sh-rules, sh-smie--rc-newline-semi-p): New functions.
(sh-set-shell): Use smie-setup if requested.