(latex-metasection-list): New var.

(latex-metasection-list): New var.
(latex-imenu-create-index): Use it.
Move the regexp construction outside loops (and use push).
(tex-font-lock-keywords-1, tex-font-lock-keywords-2)
(tex-font-lock-keywords): Moved from font-lock.el.
(tex-comment-indent): Remove.
(tex-common-initialization): Don't set comment-indent-function.
(latex-block-default): New var.
(tex-latex-block): Use it to provide a default choice.
Add any unknown choice to latex-block-names.
Insert [...] after {...}.
(tex-last-unended-begin): Simplify regexp.
(tex-goto-last-unclosed-latex-block, latex-backward-sexp-1)
(latex-forward-sexp-1, latex-forward-sexp): New functions.
(latex-mode): Set forward-sexp-function.