Fix and improve last syntax-propertize patch

Fix and improve last syntax-propertize patch
* lisp/emacs-lisp/syntax.el (syntax-propertize-precompile-rules): New macro.
(syntax-propertize-rules): Add var-ref case.  Fix offset computation
when adding surrounding \(..\).

* lisp/progmodes/fortran.el (fortran--font-lock-syntactic-keywords): Remove.
(fortran-make-syntax-propertize-function): New function; replaces
fortran-font-lock-syntactic-keywords.
(fortran-mode): Use it.
(fortran-line-length): Use it.  Improve interactive spec.

* lisp/progmodes/js.el (js-mode): Fix last change (bug#7054).

* lisp/textmodes/tex-mode.el (tex-syntax-propertize-rules)
(latex-syntax-propertize-rules): New consts; replace
tex-font-lock-syntactic-keywords.
(tex-env-mark, latex-env-before-change): New functions.
(latex-electric-env-pair-mode): New minor mode.
(tex-font-lock-verb): Change arguments; do move point.
(tex-font-lock-syntactic-face-function): Adjust to new verbatim
representation as a form of comment.
(tex-font-lock-keywords-1): Remove workaround, now unneeded.
(doctex-syntax-propertize-rules): New const; replaces
doctex-font-lock-syntactic-keywords.
(tex-common-initialization, doctex-mode): Use syntax-propertize-rules.