(sh-mode-default-syntax-table): Renamed from sh-mode-syntax-table.

(sh-mode-default-syntax-table): Renamed from sh-mode-syntax-table.
Call sh-mode-syntax-table directly.
(sh-mode-syntax-table-input): New variable.
(sh-require-final-newline): Don't use eval.
(sh-builtins, sh-leading-keywords, sh-other-keywords)
(sh-variables, sh-font-lock-keywords): Don't use eval.
(sh-set-shell): When setting require-final-newline,
treat value = `require-final-newline' as don't change it.
Set sh-mode-syntax-table locally based on
sh-mode-syntax-table-input and sh-mode-default-syntax-table.