(sh-font-lock-syntactic-keywords): Handle here-docs differently.

(sh-font-lock-syntactic-keywords): Handle here-docs differently.
(sh-font-lock-heredoc): Remove.
(sh-here-doc-open-re, sh-here-doc-markers, sh-here-doc-re): New vars.
(sh-font-lock-here-doc, sh-font-lock-close-heredoc)
(sh-font-lock-open-heredoc): New functions.
(sh-mode): Don't copy sh-font-lock-syntactic-keywords any more.
(sh-font-lock-keywords-1): Use regexp-opt.
(sh-in-comment-or-string): Use syntax-ppss.
(sh-case, sh-for, sh-indexed-loop, sh-function, sh-if, sh-repeat)
(sh-select, sh-tmp-file): Add explicit terminating \n.